Head trauma results in manyfold increased risk of multiple sclerosis in genetically susceptible individuals.

BACKGROUND: Large register-based studies have reported an association between head trauma and increased risk of multiple sclerosis (MS). We aimed to investigate possible interactions between head trauma and MS-associated HLA genes in relation to MS risk. METHODS: We used a Swedish population-based case-control study (2807 incident cases, 5950 matched controls with HLA genotypes available for 2057 cases, 2887 controls). Subjects with and without a history of self-reported head trauma were compared regarding MS risk, by calculating ORs with 95% CIs using logistic regression models. Additive interaction between head trauma, HLA-DRB1*1501 and absence of HLA-A*0201, was assessed by calculating the attributable proportion (AP) due to interaction. RESULTS: A history of head trauma was associated with a 30% increased risk of subsequently developing MS (OR 1.34, 95% CI 1.17 to 1.53), with a trend showing increased risk of MS with increasing number of head impacts (p=0.03). We observed synergistic effects between recent head trauma and HLA-DRB1*15:01 as well as absence of HLA*02:01 in relation to MS risk (each AP 0.40, 95% CI 0.1 to 0.7). Recent head trauma in individuals with both genetic risk factors rendered an 18-fold increased risk of MS, compared with those with neither the genetic risk factors nor a history of head trauma (OR 17.7, 95% CI 7.13 to 44.1). CONCLUSIONS: Our findings align with previous observations of a dose-dependent association between head trauma and increased risk of MS and add a novel aspect of this association by revealing synergistic effects between recent head trauma and MS-associated HLA genes.

Predictive validity of a selection instrument measuring resilience: The INSPIRE resilience scale.

Military personnel needs to be resilient to be able to remain effective, motivated, and in good mental and physical health. Military organizations select on resilience to determine whether candidates are psychologically fit for their job. The INSPIRE Resilience Scale (IRS) is such a selection instrument that aims to assess the psychological resilience potential of candidates in high-risk professions. A longitudinal predictive validity study was conducted in five European Defense organizations and in the Dutch National Police. The IRS was submitted in selection (N = 11,404), and criterion data about performance and health were collected in the second half of the first training year (N = 726). The results based on correlational and regression analyses showed that the IRS scores significantly predicted the criterion measures. Emotional stability, part of the IRS, turned out to be the best predictor. Results also showed that candidates who dropped out of training had significantly lower means on the IRS in selection than candidates who were still in training in the second half of the first training year. Overall, the IRS proved to be a valid instrument to assess resilience potential in candidates for high-risk professions. Selecting on resilience may therefore contribute to training success and reduction of health problems.

A factor VIIIa-mimetic bispecific antibody, Mim8, ameliorates bleeding upon severe vascular challenge in hemophilia A mice.

Hemophilia A is a bleeding disorder resulting from deficient factor VIII (FVIII), which normally functions as a cofactor to activated factor IX (FIXa) that facilitates activation of factor X (FX). To mimic this property in a bispecific antibody format, a screening was conducted to identify functional pairs of anti-FIXa and anti-FX antibodies, followed by optimization of functional and biophysical properties. The resulting bispecific antibody (Mim8) assembled efficiently with FIXa and FX on membranes, and supported activation with an apparent equilibrium dissociation constant of 16 nM. Binding affinity with FIXa and FX in solution was much lower, with equilibrium dissociation constant values for FIXa and FX of 2.3 and 1.5 µM, respectively. In addition, the activity of Mim8 was dependent on stimulatory activity contributed by the anti-FIXa arm, which enhanced the proteolytic activity of FIXa by 4 orders of magnitude. In hemophilia A plasma and whole blood, Mim8 normalized thrombin generation and clot formation, with potencies 13 and 18 times higher than a sequence-identical analogue of emicizumab. A similar potency difference was observed in a tail vein transection model in hemophilia A mice, whereas reduction of bleeding in a severe tail-clip model was observed only for Mim8. Furthermore, the pharmacokinetic parameters of Mim8 were investigated and a half-life of 14 days shown in cynomolgus monkeys. In conclusion, Mim8 is an activated FVIII mimetic with a potent and efficacious hemostatic effect based on preclinical data.

Identification of a Small Translocation from 6R Possessing Stripe Rust Resistance to Wheat.

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici Eriks. & E. Henn, is the most devastating fungal disease of bread wheat. Here, a wheat-rye multiple disomic substitution line, SLU126 4R (4D), 5R (5D), and 6R (7D), possessing resistance against 25 races of P. striiformis f. sp. tritici, was used and crossed with Chinese Spring ph1b to induce homeologous recombination to produce introgressions with a reduced rye chromosome segment. Seedling assays confirmed that the stripe rust resistance from SLU126 was retained over multiple generations. Through genotyping-by-sequencing (GBS) platforms and aligning the putative GBS-single-nucleotide polymorphism (SNPs) to the full-length annotated rye nucleotide-binding leucine-rich repeat (NLR) genes in the parental lines (CS ph1b, SLU126, CSA, and SLU820), we identified the physical position of 26, 13, and 9 NLR genes on chromosomes 6R, 4R, and 5R, respectively. The physical positions of 25 NLR genes on chromosome 6R were identified from 568,460,437 bp to 879,958,268 bp in the 6RL chromosome segment. Based on these NLR positions on the 6RL chromosome segment, the three linked SNPs (868,123,650 to 873,285,112 bp) were validated through kompetitive allele-specific PCR (KASP) assays in SLU126 and resistance plants in the family 29-N3-5. Using these KASP markers, we identified a small piece of the rye translocation (i.e., as a possible 6DS.6DL.6RL.6DL) containing the stripe resistance gene, temporary designated YrSLU, within the 6RL segment. This new stripe rust resistance gene provides an additional asset for wheat improvement to mitigate yield losses caused by stripe rust.

Metabolic Processes and Biological Macromolecules Defined the Positive Effects of Protein-Rich Biostimulants on Sugar Beet Plant Development.

Protein-based biostimulants (PBBs) have a positive effect on plant development, although the biological background for this effect is not well understood. Here, hydrolyzed wheat gluten (HWG) and potato protein film (PF) in two levels (1 and 2 g/kg soil) and in two different soils (low and high nutrient; LNC and HNC) were used as PBBs. The effect of these PBBs on agronomic traits, sugars, protein, and peptides, as well as metabolic processes, were evaluated on sugar beet in comparison with no treatment (control) and treatment with nutrient solution (NS). The results showed a significant growth enhancement of the plants using HWG and PF across the two soils. Sucrose and total sugar content in the roots were high in NS-treated plants and correlated to root growth in HNC soil. Traits related to protein composition, including nitrogen, peptide, and RuBisCO contents, were enhanced in PBB-treated plants (mostly for HWG and PF at 2 g/kg soil) by 100% and >250% in HNC and LNC, respectively, compared to control. The transcriptomic analysis revealed that genes associated with ribosomes and photosynthesis were upregulated in the leaf samples of plants treated with either HWG or PP compared to the control. Furthermore, genes associated with the biosynthesis of secondary metabolites were largely down-regulated in root samples of HWG or PF-treated plants. Thus, the PBBs enhanced protein-related traits in the plants through a higher transcription rate of genes related to protein- and photosynthesis, which resulted in increased plant growth, especially when added in certain amounts (2 g/kg soil). However, sucrose accumulation in the roots of sugar beet seemed to be related to the easy availability of nitrogen.

Sustainable Wheat Protein Biofoams: Dry Upscalable Extrusion at Low Temperature.

Glycerol-plasticized wheat gluten was explored for producing soft high-density biofoams using dry upscalable extrusion (avoiding purposely added water). The largest pore size was obtained when using the food grade ammonium bicarbonate (ABC) as blowing agent, also resulting in the highest saline liquid uptake. Foams were, however, also obtained without adding a blowing agent, possibly due to a rapid moisture uptake by the dried protein powder when fed to the extruder. ABC's low decomposition temperature enabled extrusion of the material at a temperature as low as 70 °C, well below the protein aggregation temperature. Sodium bicarbonate (SBC), the most common food-grade blowing agent, did not yield the same high foam qualities. SBC's alkalinity, and the need to use a higher processing temperature (120 °C), resulted in high protein cross-linking and aggregation. The results show the potential of an energy-efficient and industrially upscalable low-temperature foam extrusion process for competitive production of sustainable biofoams using inexpensive and readily available protein obtained from industrial biomass (wheat gluten).

Climate Change Impact on Wheat Performance-Effects on Vigour, Plant Traits and Yield from Early and Late Drought Stress in Diverse Lines.

Global climate change is threatening wheat productivity; improved yield under drought conditions is urgent. Here, diverse spring-wheat lines (modern, old and wheat-rye introgressions) were examined in an image-based early-vigour assay and a controlled-conditions (Biotron) trial that evaluated 13 traits until maturity. Early root vigour was significantly higher in the old Swedish lines (root length 8.50 cm) and introgressed lines with 1R (11.78 cm) and 1RS (9.91 cm) than in the modern (4.20 cm) and 2R (4.67 cm) lines. No significant correlation was noted between early root and shoot vigour. A higher yield was obtained under early drought stress in the 3R genotypes than in the other genotype groups, while no clear patterns were noted under late drought. Evaluating the top 10% of genotypes in terms of the stress-tolerance index for yield showed that root biomass, grains and spikes per plant were accountable for tolerance to early drought, while 1000-grain weight and flag-leaf area were accountable for tolerance to late drought. Early root vigour was determined as an important focus trait of wheat breeding for tolerance to climate-change-induced drought. The responsible genes for the trait should be searched for in these diverse lines. Additional drought-tolerance traits determined here need further elaboration to identify the responsible genes.

Innovatively processed quinoa (Chenopodium quinoa Willd.) food: chemistry, structure and end-use characteristics.

BACKGROUND: Quinoa (Chenopodium quinoa Willd.) flour and processed traditional Peruvian quinoa breakfast foods were studied to evaluate the effect of extrusion and post-processing on protein properties, morphology and nutritional characteristics (amino acids and dietary fibers). RESULTS: The extrusion increased quinoa protein crosslinking and aggregation observed by size exclusion high-performance liquid chromatography and the amount of soluble fibers, as well as decreasing the amounts of insoluble fibers in the processed foods. The post-processing drying resulted in additional crosslinking of large protein fractions in the quinoa products. The microstructure of the extruded quinoa breakfast flakes and heat-post-processed samples studied by scanning electron microscopy and X-ray tomography differed greatly; post-drying induced formation of aerated protein microstructures in the heat-treated samples. Nanostructures revealed by small-angle and wide-angle X-ray scattering indicated that extrusion imparted morphological changes in the quinoa protein and starch (dominance of V-type). Overall, extrusion processing only reduced the content of most of the essential amino acids to a minor extent; the content of valine and methionine was reduced to a slightly greater extent, but the final products met the requirements of the Food and Drug Organization. CONCLUSION: This study presents innovative examples on how extrusion processing and post-processing heat treatment can be used to produce attractive future food alternatives, such as breakfast cereal flakes and porridge powder, from quinoa grains. Extrusion of quinoa flour into Peruvian foods was shown to be mostly impacted by the processing temperature and processing conditions used. Protein crosslinking increased due to extrusion and post-processing heating. Starch crystallinity decreased most when the product was dried after processing. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Cell free protein synthesis versus yeast expression - A comparison using insulin as a model protein.

Expression of recombinant proteins traditionally require a cellular system to transcribe and translate foreign DNA to a desired protein. The process requires special knowledge of the specific cellular metabolism in use and is often time consuming and labour intensive. A cell free expression system provides an opportunity to express recombinant proteins without consideration of the living cell. Instead, a cell free system relies on either a cellular lysate or recombinant proteins to carry out protein synthesis, increasing overall production speed and ease of handling. The one-pot cell free setup is commonly known as an in vitro transcription/translation reaction (IVTT). Here we focused on a PURE (Protein synthesis Using Recombinant Elements) IVTT system based on recombinant proteins from Escherichia coli. We evaluated the cell free system's ability to express functional insulin analogues compared to Saccharomyces cerevisiae, a well-established system for large scale production of recombinant human insulin and insulin analogues. Significantly, it was found that correct insulin expression and folding was governed by the inherent properties of the primary amino acids sequence of insulin, whereas the eukaryotic features of the expression system apparently play a minor role. The IVTT system successfully produced insulin analogues identical in structure and with similar insulin receptor affinity to those produced by yeast. In conclusion we demonstrate that the PURE IVTT system is highly suited for expressing soluble molecules with higher order features and multiple disulphide bridges.

Lupin Protein Isolate Structure Diversity in Frozen-Cast Foams: Effects of Transglutaminases and Edible Fats.

This study addresses an innovative approach to generate aerated foods with appealing texture through the utilization of lupin protein isolate (LPI) in combination with edible fats. We show the impact of transglutaminases (TGs; SB6 and commercial), glycerol (Gly), soy lecithin (Lec) and linoleic acid (LA) on the micro- and nanostructure of health promoting solid foods created from LPI and fats blends. 3-D tomographic images of LPI with TG revealed that SB6 contributed to an exceptional bubble spatial organization. The inclusion of Gly and Lec decreased protein polymerization and also induced the formation of a porous layered material. LA promoted protein polymerization and formation of homogeneous thick layers in the LPI matrix. Thus, the LPI is a promising protein resource which when in blend with additives is able to create diverse food structures. Much focus has been placed on the great foamability of LPI and here we show the resulting microstructure of LPI foams, and how these were improved with addition of TGs. New food applications for LPI can arise with the addition of food grade dispersant Lec and essential fatty-acid LA, by improved puffiness, and their contributing as replacer of chemical leavening additives in gluten-free products.

Identification of Binding Sites on Human Serum Albumin for Somapacitan, a Long-Acting Growth Hormone Derivative.

Somapacitan, a human growth hormone derivative that binds reversibly to albumin, was investigated for human serum albumin (HSA) and HSA domain binding. Isothermal titration calorimetry (ITC) binding profiles showed high-affinity binding (∼100-1000 nM) of one somapacitan molecule and low-affinity binding (∼1000-10000 nM) of one to two somapacitan molecules to HSA. The high-affinity site was identified in HSA domain III using size exclusion chromatography (SEC) and ITC. SEC studies showed that the neonatal Fc receptor shields one binding site for somapacitan, indicating its position in domain III. A crystal structure of somapacitan in complex with HSA optimized for neonatal Fc receptor binding, having four amino acid residue replacements, identified a low-affinity site in fatty acid-binding site 6 (domain II). Surface plasmon resonance (SPR) showed these replacements affect the kinetics of the high-affinity binding site. Furthermore, small-angle X-ray scattering and SPR brace two somapacitan-binding sites on HSA.

Carboxylated Wheat Gluten Proteins: A Green Solution for Production of Sustainable Superabsorbent Materials.

Functionalized wheat gluten (WG) protein particles with the ability to absorb fluids within the superabsorbent range are presented. Ethyleneditetraacetic dianhydride (EDTAD), a nontoxic acylation agent, was used for the functionalization of the WG protein at higher protein content than previously reported and no additional chemical cross-linking. The 150-550 µm protein particles had 50-150 nm nanopores induced by drying. The EDTAD treated WG were able to absorb 22, 5, and 3 times of, respectively, water, saline and blood, per gram of dry material (g/g), corresponding to 1000, 150 and 100% higher values than for the as-received WG powder. The liquid retention capacity after centrifugation revealed that almost 50% of the saline liquid was retained within the protein network, which is similar to that for petroleum-based superabsorbent polymers (SAPs). An advantageous feature of these biobased particulate materials is that the maximum swelling is obtained within the first 10 min of exposure, that is, in contrast to many commercial SAP alternatives. The large swelling in a denaturation agent (6 M urea) solution (about 32 g/g) suggests that the secondary entangled/folded structure of the protein restricts protein network expansion and when disrupted allows the absorption of even higher amounts of liquid. The increased liquid uptake, utilization of inexpensive protein coproducts, easy scalable protocols, and absence of any toxic chemicals make these new WG-based SAP particles an interesting alternative to petroleum-based SAP in, for example, absorbent disposable hygiene products.

Changes in lifestyle among prostate cancer survivors: A nationwide population-based study.

OBJECTIVE: Long-term information on lifestyle changes among prostate survivors is lacking. In this nationwide, population-based study we investigated the prevalence of lifestyle changes, factors associated with lifestyle changes and associations between lifestyle changes and general quality of life. METHODS: All men registered in the National Prostate Cancer Register of Sweden diagnosed in 2008 with low-risk prostate cancer at age 70 years or younger were sent a questionnaire. Logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals for factors potentially associated with lifestyle change. RESULTS: Out of 1288, 1720 men (75%) were responded. A total of 279 (22%) reported a positive lifestyle change regarding diet or exercise. Poor functional outcomes after treatment was associated with exercising less (OR 1.6, 95% CI 1.2-2.1) and less interest in social activities and relationships (OR 1.8, 95% CI 1.5-2.1). Men who exercised more (OR 7.9, 95% CI 4.4-14) and men who had an increased interest in relationships and social activities (OR 5.2, 95% CI 2.1-13) reported higher general quality of life. CONCLUSIONS: A considerable proportion of men reported making positive lifestyle changes after the prostate cancer diagnosis. The time after diagnosis may be a teachable moment that facilitates lifestyle interventions. Poor functional outcomes after treatment may reduce the willingness to engage in positive lifestyle change, which need be considered when supporting men after treatment. Men who made a positive lifestyle change, regardless of whether it was exercise or regarding relationships and social activities more often reported a high level of general quality of life.

Modeling to Understand Plant Protein Structure-Function Relationships-Implications for Seed Storage Proteins.

Proteins are among the most important molecules on Earth. Their structure and aggregation behavior are key to their functionality in living organisms and in protein-rich products. Innovations, such as increased computer size and power, together with novel simulation tools have improved our understanding of protein structure-function relationships. This review focuses on various proteins present in plants and modeling tools that can be applied to better understand protein structures and their relationship to functionality, with particular emphasis on plant storage proteins. Modeling of plant proteins is increasing, but less than 9% of deposits in the Research Collaboratory for Structural Bioinformatics Protein Data Bank come from plant proteins. Although, similar tools are applied as in other proteins, modeling of plant proteins is lagging behind and innovative methods are rarely used. Molecular dynamics and molecular docking are commonly used to evaluate differences in forms or mutants, and the impact on functionality. Modeling tools have also been used to describe the photosynthetic machinery and its electron transfer reactions. Storage proteins, especially in large and intrinsically disordered prolamins and glutelins, have been significantly less well-described using modeling. These proteins aggregate during processing and form large polymers that correlate with functionality. The resulting structure-function relationships are important for processed storage proteins, so modeling and simulation studies, using up-to-date models, algorithms, and computer tools are essential for obtaining a better understanding of these relationships.

Population-based, nationwide registration of prostatectomies in Sweden.

INTRODUCTION: Radical prostatectomy (RP) is a common surgical procedure with a risk of postoperative erectile dysfunction and urinary incontinence. There is a need for data on RP as a basis for quality assurance and benchmarking. METHODS: In 2015, prostatectomies in Sweden (PiS) form was implemented in the National Prostate Cancer Register (NPCR) of Sweden with data on pre-, peri- and post-operative variables. RESULTS: Out of all radical prostatectomies performed in 2016 in Sweden, 3096/3881 (80%) were registered in PiS. A total of 2605 (84%) were robot-assisted radical prostatectomy (RARP) and 491 (16%) were RRP (retropubic radical prostatectomy). RARP was performed by 91 surgeons of whom 47% operated more than 25 RP/year; and RRP was performed by 69 surgeons of whom 10% performed more than 25 RP/year. RARP had a longer operative time (median operating time: RARP 155 minutes [IQR 124-190]; RRP 129 minutes [IQR 105-171]; P < .001) but was associated with smaller bleeding (median intraoperative blood loss: RARP 100 mL [IQR 50-200], RRP 700 mL [IQR 500-1100]; P < .001). CONCLUSIONS: We report on a nationwide, population-based register with transparent reporting of data on the performance of radical prostatectomy. These data are needed as a basis for quality assurance with comparisons of results from individual surgeons and hospitals.

Nationwide, population-based study of post radical prostatectomy urinary incontinence correction surgery.

OBJECTIVES: To assess the use of post radical prostatectomy (RP) urinary incontinence (PPI) surgery and to investigate factors related to its use. METHODS: Cohort study in Prostate Cancer database Sweden (PCBaSe) of men who underwent primary RP between 1998 and 2012. PPI correction procedures were identified in the Patient Registry. Hazard ratios (HR) and 95% confidence intervals (CIs) of PPI surgeries were estimated. RESULTS: Seven hundred eighty-two out of 26 280 (3%) men underwent PPI surgery at a median time of 3 years after RP. There was an eightfold increase in the absolute number of PPI surgeries during 2000-2014 and a threefold increase in the number per 1000 RPs performed. Factors associated with high use PPI surgery were age >70, HR 1.96 (1.54-2.50), and high hospital RP volume (>100 RPs/year), HR 0.81 (0.66-0.99). There was a 10-fold difference in use of PPI surgery per 1000 RPs between the county with the highest versus lowest use. In a subgroup of men with Patient-Reported Outcome Measures (PROM); severe PPI was reported by 7% of men and 24% of them underwent PPI surgery. CONCLUSIONS: Three percent of all men received PPI surgery, with a 10-fold variation among health care providers. Only a quarter of men with severe PPI underwent PPI surgery, suggesting that PPI surgery remains underutilized.

A transnational and holistic breeding approach is needed for sustainable wheat production in the Baltic Sea region.

The Baltic Sea is one of the largest brackish water bodies in the world. Eutrophication is a major concern in the Baltic Sea due to the leakage of nutrients to the sea with agriculture being the primary source. Wheat (Triticum aestivum L.) is the most widely grown crop in the countries surrounding the Baltic Sea and thus promoting sustainable agriculture practices for wheat cultivation will have a major impact on reducing pollution in the Baltic Sea. This approach requires identifying and addressing key challenges for sustainable wheat production in the region. Implementing new technologies for climate-friendly breeding and digital farming across all surrounding countries should promote sustainable intensification of agriculture in the region. In this review, we highlight major challenges for wheat cultivation in the Baltic Sea region and discuss various solutions integrating transnational collaboration for pre-breeding and technology sharing to accelerate development of low input wheat cultivars with improved host plant resistance to pathogen and enhanced adaptability to the changing climate.

Occupational status among adult survivors following allogeneic stem cell transplantation in childhood.

This study examined occupational status and factors associated with sick leave and disability pension among adult long-term survivors previously treated with allogeneic stem cell transplantation (allo-SCT) during childhood. Moreover, occupational status was compared to that of a reference group. Data were collected with questionnaires and from medical records. The SCT group included 59 adults (18-45 years old: response rate 63%) treated with allo-SCT in childhood with a median of 17 (range 3-28) years earlier. The reference group included 296 individuals randomly selected from the general population. The results show that 54% of the long-term survivors were working part- or full-time and that 19% were on sick leave or disability pension. A larger proportion of the SCT group was on sick leave or disability pension (19% vs. 6%: p < .001) than of the reference group. The logistic regression analysis revealed that being on sick leave or disability pension among long-term survivors was associated with late effects related to the allo-SCT (OR 12.28: 95% CI 1.3-111.6: p = .03). The results underscore that long-term survivors' engagement in paid work is influenced many years after treatment and highlights the need to include vocational assistance in the rehabilitation following allo-SCT in childhood.

Impact of pH Modification on Protein Polymerization and Structure⁻Function Relationships in Potato Protein and Wheat Gluten Composites.

Wheat gluten (WG) and potato protein (PP) were modified to a basic pH by NaOH to impact macromolecular and structural properties. Films were processed by compression molding (at 130 and 150 °C) of WG, PP, their chemically modified versions (MWG, MPP) and of their blends in different ratios to study the impact of chemical modification on structure, processing and tensile properties. The modification changed the molecular and secondary structure of both protein powders, through unfolding and re-polymerization, resulting in less cross-linked proteins. The ß-sheet formation due to NaOH modification increased for WG and decreased for PP. Processing resulted in cross-linking of the proteins, shown by a decrease in extractability; to a higher degree for WG than for PP, despite higher ß-sheet content in PP. Compression molding of MPP resulted in an increase in protein cross-linking and improved maximum stress and extensibility as compared to PP at 130 °C. The highest degree of cross-linking with improved maximum stress and extensibility was found for WG/MPP blends compared to WG/PP and MWG/MPP at 130 °C. To conclude, chemical modification of PP changed the protein structures produced under harsh industrial conditions and made the protein more reactive and attractive for use in bio-based materials processing, no such positive gains were seen for WG.

Type II Turn of Receptor-bound Salmon Calcitonin Revealed by X-ray Crystallography.

Calcitonin is a peptide hormone consisting of 32 amino acid residues and the calcitonin receptor is a Class B G protein-coupled receptor (GPCR). The crystal structure of the human calcitonin receptor ectodomain (CTR ECD) in complex with a truncated analogue of salmon calcitonin ([BrPhe(22)]sCT(8-32)) has been determined to 2.1-Å resolution. Parallel analysis of a series of peptide ligands showed that the rank order of binding of the CTR ECD is identical to the rank order of binding of the full-length CTR, confirming the structural integrity and relevance of the isolated CTR ECD. The structure of the CTR ECD is similar to other Class B GPCRs and the ligand binding site is similar to the binding site of the homologous receptors for the calcitonin gene-related peptide (CGRP) and adrenomedulin (AM) recently published (Booe, J. M., Walker, C. S., Barwell, J., Kuteyi, G., Simms, J., Jamaluddin, M. A., Warner, M. L., Bill, R. M., Harris, P. W., Brimble, M. A., Poyner, D. R., Hay, D. L., and Pioszak, A. A. (2015) Mol. Cell 58, 1040-1052). Interestingly the receptor-bound structure of the ligand [BrPhe(22)]sCT(8-32) differs from the receptor-bound structure of the homologous ligands CGRP and AM. They all adopt an extended conformation followed by a C-terminal ß turn, however, [BrPhe(22)]sCT(8-32) adopts a type II turn (Gly(28)-Thr(31)), whereas CGRP and AM adopt type I turns. Our results suggest that a type II turn is the preferred conformation of calcitonin, whereas a type I turn is the preferred conformation of peptides that require RAMPs; CGRP, AM, and amylin. In addition the structure provides a detailed molecular explanation and hypothesis regarding ligand binding properties of CTR and the amylin receptors.