Functional and biochemical characterisation of remote homologues of type IV pili proteins PilN and PilO in Helicobacter pylori.

Helicobacter pylori encodes homologues of PilM, PilN and PilO from bacteria with Type IV pili, where these proteins form a pilus alignment complex. Inactivation of pilO changes H. pylori motility in semi-solid media, suggesting a link to the chemosensory pathways or flagellar motor. Here, we showed that mutation of the pilO or pilN gene in H. pylori strain SS1 reduced the mean linear swimming speed in liquid media, implicating PilO and PilN in the function, or regulation of, the flagellar motor. We also demonstrated that the soluble variants of H. pylori PilN and PilO share common biochemical properties with their Type IV pili counterparts which suggests their adapted function in the bacterial flagellar motor may be similar to that in the Type IV pili.

Characterization of a New, Country Bean (Lablab purpureus) Lineage of Bean Common Mosaic Necrosis Virus.

Country bean (Lablab purpureus, family Fabaceae) is grown in subsistence agriculture in Bangladesh as a multipurpose crop for food, animal feed, and green manure. This study was undertaken to investigate the genetic diversity of bean common mosaic necrosis virus (BCMNV, genus Potyvirus, family Potyviridae) in country beans. Leaf samples from country beans showing yellowing, vein banding, and mosaic symptoms were collected during field surveys between 2015 and 2019 cropping seasons from farmers' fields in different geographic regions. These samples were tested by serological and molecular diagnostic assays for the presence of BCMNV. Virus-positive samples were subjected to high-throughput Illumina sequencing to generate near-complete genomes of BCMNV isolates. In pairwise comparisons, the polyprotein sequences of BCMNV isolates from Bangladesh showed greater than 98% identities among themselves and shared less than 84% sequence identity at the nucleotide level with virus isolates reported from other countries. In the phylogenetic analysis, BCMNV isolates from Bangladeshi country beans formed a separate clade from virus isolates reported from common beans in other countries in the Americas, Africa, Europe, and from East Timor. Grow-out studies showed seed-to-seedling transmission of BCMNV, implying a possible seedborne nature of the virus in country beans.

Extragenital Sexually Transmitted Infection Testing Among Louisiana Parish Health Units, 2016-2019.

BACKGROUND: The Centers for Disease Control and Prevention recommends that men who have sex with men (MSM) get tested annually for urethral and rectal chlamydia (CT) and gonorrhea (NG), and pharyngeal NG. There are no national recommendations to screen women and heterosexual men at extragenital sites. We assessed extragenital CT/NG screening among men and women at Louisiana's Parish Health Units (PHU). METHODS: The Louisiana STD/HIV/Hepatitis Program piloted extragenital screening at 4 PHUs in February 2016 and expanded to 11 PHUs in 2017. Sexual histories were used to identify gender of sex partners and exposed sites. Because of billing restrictions, up to 2 anatomical sites were tested for CT/NG. RESULTS: From February 2016 to June 2019, 70,895 urogenital and extragenital specimens (56,086 urogenital, 13,797 pharyngeal, and 1,012 rectal) were collected from 56,086 patients. Pharyngeal CT positivity was 160 of 7,868 (2.0%) among women, 54 of 4,838 (1.1%) among men who have sex with women (MSW) and 33 of 1,091 (3.0%) among MSM. Rectal CT positivity was 51 of 439 (11.6%) among women and 95 of 573 (16.6%) among MSM. Pharyngeal NG positivity was 299 of 7,868 (3.8%) among women, 222 of 4,838 (4.6%) among MSW, and 97 of 1,091 (8.9%) among MSM. Rectal NG positivity was 20 of 439 (4.6%) among women and 134 of 573 (23.4%) among MSM.Urogenital-only screening would have missed: among women, 173 of 3,923 (4.4%) CT and 227 of 1,480 (15.3%) NG infections; among MSW, 26 of 2,667 (1%) CT and 149 of 1,709 (8.7%) NG infections; and among MSM, 116 of 336 (34.5%) CT and 127 of 413 (42.1%) NG infections. CONCLUSIONS: Many CT/NG infections would have been missed with urogenital-only screening. Men who have sex with men had much higher extragenital infection rates than women and MSW.

Molecular Recognition of Methacryllysine and Crotonyllysine by the AF9 YEATS Domain.

Histone lysine methacrylation and crotonylation are epigenetic marks that play important roles in human gene regulation. Here, we explore the molecular recognition of histone H3 peptides possessing methacryllysine and crotonyllysine at positions 18 and 9 (H3K18 and H3K9) by the AF9 YEATS domain. Our binding studies demonstrate that the AF9 YEATS domain displays a higher binding affinity for histones possessing crotonyllysine than the isomeric methacryllysine, indicating that AF9 YEATS distinguishes between the two regioisomers. Molecular dynamics simulations reveal that the crotonyllysine/methacryllysine-mediated desolvation of the AF9 YEATS domain provides an important contribution to the recognition of both epigenetic marks. These results provide important knowledge for the development of AF9 YEATS inhibitors, an area of biomedical interest.

Electronic Messaging for Gonorrhea and Chlamydia Test Result Notification, Improving Treatment and Patient Satisfaction.

BACKGROUND: Approximately 20% of chlamydia (CT) and gonorrhea (GC) cases in Louisiana are diagnosed at Parish Health Units. Patient notification of CT and GC test results involves nurses' phone calls and letters to positive patients, which is time-consuming and inefficient. METHODS: In December 2018, electronic results notification was implemented in Caddo Parish Health Unit using Chexout software to notify enrolled patients via text or email when test results are ready to view in a patient portal. We compared the timeliness of GC/CT results notification and treatment pre-Chexout (December 2017 to November 2018) and post-Chexout (December 2018 to November 2019) implementation. A random sample of patients was interviewed to assess acceptability. RESULTS: During December 2018 to November 2019, 5432 patients were tested for CT/GC, 3924 (72%) enrolled in Chexout, and notifications were sent to 3884 (99%). Among CT-positives, 472 of 568 (83%) viewed results in the portal compared with 2451 of 3356 (73%) CT-negatives. Among GC-positives, 300 of 353 (85%) viewed results compared with 2657 of 3571 (74%) GC-negatives. Treatment success for CT improved from 493 of 670 (74%) to 506 of 568 (89%), and for GC, from 332 of 409 (81%) to 325 of 353 (92%). Mean time to treatment decreased for CT (13.4-10.7 days) and GC (11.3-9.2 days). Enrolled patients found Chexout notification satisfactory in 168 of 169 (99%) and easy to use in 130 of 141 (92%). Reasons for declining electronic notification included lack of personal cell phone for 55 of 86 (64%) and confidentiality concerns for 42 of 86 (49%). CONCLUSIONS: Electronic messaging decreased time to notification and increased treatment success. Nurses spent less time notifying patients leaving more time for patient care.

Hepatitis E virus genotype 1f outbreak in Bangladesh, 2018.

Hepatitis E virus (HEV) infection is a significant public health issue in many developing countries, causing waterborne outbreaks as well as sporadic hepatitis. We report here an outbreak of HEV genotype 1f infection during April-May 2018 among people living at Halisohor, a low land in the southern part of Chottogram District of Bangladesh. A total of 933 patients were admitted to Combined Military Hospital (CMH), Chottogram, with symptoms of acute hepatitis. Among them, 550 patients were tested by ELISA for HEV-specific (IgM) and all were positive. Genotyping, sequencing, and phylogenetic analysis based on ORF2 region revealed that the outbreak was caused by genotype 1f and the strains were closely related to the previously reported HEV strains that caused the outbreak in Bangladesh in 2010. The current outbreak was most likely linked with water supply as fecal contamination in water was evident and could be prevented by ensuring access to safe drinking water.

Rates of New Human Immunodeficiency Virus (HIV) Diagnoses After Reported Sexually Transmitted Infection in Women in Louisiana, 2000-2015: Implications for HIV Prevention.

BACKGROUND: Human immunodeficiency virus (HIV) prevention interventions for prevention interventions for women include screening, partner notification, promoting condoms, and preexposure prophylaxis (PrEP). Women's risk of acquiring HIV can help guide recommendations. METHODS: We used data from Louisiana's sexually transmitted infection (STI) and HIV registries to study 13- to 59-year-old women following first diagnosis of syphilis, gonorrhea, or chlamydia during 2000-2015. We measured HIV rates reported subsequent to STI (through 2016). Rates for women without STI were estimated by subtracting women with STI from reported cases and from Census estimates for the population. PrEP cost was estimated as $11 000 per year, and effectiveness estimated as 100%. RESULTS: STIs were syphilis (6574), gonorrhea (64 995), or chlamydia (140 034). These 211 603 women had 1 865 488 person-years of follow-up and 969 HIV diagnoses. Women with no STI had 5186 HIV diagnoses over 24 359 397 person-years. HIV rates diagnosis (per 100 000 person-years) were higher for women after syphilis (177.3), gonorrhea (73.2), or chlamydia (35.4) compared to women with no STI (22.4). Providing PrEP to all women diagnosed with syphilis or gonorrhea would cost $7 371 111 000 and could have prevented 546 HIV diagnoses. Limiting PrEP to 1 year after syphilis or gonorrhea diagnosis would cost $963 847 334, but only 143 HIV diagnoses were within 2 years after a syphilis or gonorrhea diagnosis. CONCLUSIONS: Rates of HIV diagnosis were high after women had STI, but not high enough to make PrEP cost-effective for them. Most women diagnosed with HIV did not have previously reported STI.

Biocompatible functionalisation of nanoclays for improved environmental remediation.

Among the wide range of materials used for remediating environmental contaminants, modified and functionalised nanoclays show particular promise as advanced sorbents, improved dispersants, or biodegradation enhancers. However, many chemically modified nanoclay materials are incompatible with living organisms when they are used in natural systems with detrimental implications for ecosystem recovery. Here we critically review the pros and cons of functionalised nanoclays and provide new perspectives on the synthesis of environmentally friendly varieties. Particular focus is given to finding alternatives to conventional surfactants used in modified nanoclay products, and to exploring strategies in synthesising nanoclay-supported metal and metal oxide nanoparticles. A large number of promising nanoclay-based sorbents are yet to satisfy environmental biocompatibility in situ but opportunities are there to tailor them to produce "biocompatible" or regenerative/reusable materials.

Molecular Basis of Unexpected Specificity of ABC Transporter-Associated Substrate-Binding Protein DppA from Helicobacter pylori.

The gastric pathogen Helicobacter pylori has limited ability to use carbohydrates as a carbon source, relying instead on exogenous amino acids and peptides. Uptake of certain peptides by H. pylori requires an ATP binding cassette (ABC) transporter annotated dipeptide permease (Dpp). The transporter specificity is determined by its cognate substrate-binding protein DppA, which captures ligands in the periplasm and delivers them to the permease. Here, we show that, unlike previously characterized DppA proteins, H. pylori DppA binds, with micromolar affinity, peptides of diverse amino acid sequences ranging between two and eight residues in length. We present analysis of the 1.45-Å-resolution crystal structure of its complex with the tetrapeptide STSA, which provides a structural rationale for the observed broad specificity. Analysis of the molecular surface revealed a ligand-binding pocket that is large enough to accommodate peptides of up to nine residues in length. The structure suggests that H. pylori DppA is able to recognize a wide range of peptide sequences by forming interactions primarily with the peptide main chain atoms. The loop that terminates the peptide-binding pocket in DppAs from other bacteria is significantly shorter in the H. pylori protein, providing an explanation for its ability to bind longer peptides. The subsites accommodating the two N-terminal residues of the peptide ligand make the greatest contribution to the protein-ligand binding energy, in agreement with the observation that dipeptides bind with affinity close to that of longer peptides.IMPORTANCE The World Health Organization listed Helicobacter pylori as a high-priority pathogen for antibiotic development. The potential of using peptide transporters in drug design is well recognized. We discovered that the substrate-binding protein of the ABC transporter for peptides, termed dipeptide permease, is an unusual member of its family in that it directly binds peptides of diverse amino acid sequences, ranging between two and eight residues in length. We also provided a structural rationale for the observed broad specificity. Since the ability to import peptides as a source of carbon is critical for H. pylori, our findings will inform drug design strategies based on inhibition or fusion of membrane-impermeant antimicrobials with peptides.

Anti-Helicobacter pylori activity of ethoxzolamide.

Ethoxzolamide (EZA), acetazolamide, and methazolamide are clinically used sulphonamide drugs designed to treat non-bacteria-related illnesses (e.g. glaucoma), but they also show antimicrobial activity against the gastric pathogen Helicobacter pylori. EZA showed the highest activity, and was effective against clinical isolates resistant to metronidazole, clarithromycin, and/or amoxicillin, suggesting that EZA kills H. pylori via mechanisms different from that of these antibiotics. The frequency of single-step spontaneous resistance acquisition by H. pylori was less than 5 × 10-9, showing that resistance to EZA does not develop easily. Resistance was associated with mutations in three genes, including the one that encodes undecaprenyl pyrophosphate synthase, a known target of sulphonamides. The data indicate that EZA impacts multiple targets in killing H. pylori. Our findings suggest that developing the approved anti-glaucoma drug EZA into a more effective anti-H. pylori agent may offer a faster and cost-effective route towards new antimicrobials with a novel mechanism of action.

Mesoporous magnetic silica particles modified with stimuli-responsive P(NIPAM-DMA) valve for controlled loading and release of biologically active molecules.

Mesoporous magnetic silica particles bearing a stimuli-responsive polymer valve were prepared and their performance as a microcapsule was evaluated. In this study, first, mesoporous magnetic iron oxide (Fe3O4) particles were prepared by a solvothermal method. Then, the magnetic particles were coated with silica and functionalized with vinyl groups using 3-(trimethoxysilyl)-propyl methacrylate (MPS). Subsequently, the Fe3O4/SiO2 composite particles grafted with MPS were used to carry out the seeded precipitation copolymerization of N-isopropylacrylamide (NIPAM) and 2,2-dimethylaminoethyl methacrylate (DMA). Here N,N'-methylenebisacrylamide (MBA) was used as a cross-linker. Brunauer-Emmett-Teller (BET) surface analysis suggested that the mesoporous structure was retained in the final Fe3O4/SiO2/P(NIPAM-DMA-MBA) composite hydrogel particles. The prepared Fe3O4/SiO2/P(NIPAM-DMA-MBA) composite hydrogel microspheres exhibited a pH-dependent volume phase transition. At lower pH values (<7), the inclusion of DMA shifted the volume phase transition to higher temperature because of the protonation of the tertiary amine groups. The composite hydrogel particles possessed a high saturation magnetization (51 emu g-1) and moved under the influence of an external magnetic field. The loading-release behaviour of these biologically active molecules suggested that a portion of the encapsulated guest molecules was released at a temperature below the lower critical solution temperature, LCST (<35 °C).

Structural basis for Myf and Psa fimbriae-mediated tropism of pathogenic strains of Yersinia for host tissues.

Three pathogenic species of the genus Yersinia assemble adhesive fimbriae via the FGL-chaperone/usher pathway. Closely related Y. pestis and Y. pseudotuberculosis elaborate the pH6 antigen (Psa), which mediates bacterial attachment to alveolar cells of the lung. Y. enterocolitica, instead, assembles the homologous fimbriae Myf of unknown function. Here, we discovered that Myf, like Psa, specifically recognizes ß1-3- or ß1-4-linked galactose in glycosphingolipids, but completely lacks affinity for phosphatidylcholine, the main receptor for Psa in alveolar cells. The crystal structure of a subunit of Psa (PsaA) complexed with choline together with mutagenesis experiments revealed that PsaA has four phosphatidylcholine binding pockets that enable super-high-avidity binding of Psa-fibres to cell membranes. The pockets are arranged as six tyrosine residues, which are all missing in the MyfA subunit of Myf. Conversely, the crystal structure of the MyfA-galactose complex revealed that the galactose-binding site is more extended in MyfA, enabling tighter binding to lactosyl moieties. Our results suggest that during evolution, Psa has acquired a tyrosine-rich surface that enables it to bind to phosphatidylcholine and mediate adhesion of Y. pestis/pseudotuberculosis to alveolar cells, whereas Myf has specialized as a carbohydrate-binding adhesin, facilitating the attachment of Y. enterocolitica to intestinal cells.

Effectiveness of Prenatal Screening and Treatment to Prevent Congenital Syphilis, Louisiana and Florida, 2013-2014.

BACKGROUND: From 2012 to 2014, rates of congenital syphilis increased in Louisiana and Florida. We evaluated the effectiveness of early (first or second) and third trimester syphilis screening for the prevention of congenital syphilis in these high-morbidity states. METHODS: Reported syphilis cases among pregnant women in Louisiana and Florida during January 1, 2013, to December 31, 2014, were reviewed for documented screening for syphilis in the first 2 trimesters and third trimester. Pregnant women with syphilis were linked to congenital syphilis records and stratified by whether the pregnancy led to a reported congenital syphilis case. RESULTS: Seven hundred ten pregnant women with syphilis in Louisiana and Florida were linked to 155 congenital syphilis cases. Three hundred seventy (52%) pregnant women with syphilis were staged as early syphilis (n = 270) or high-titer late or unknown duration-latent syphilis (n = 100), and 109 (70% of the total) were linked to congenital syphilis cases. Screening in the first 2 trimesters identified 513 pregnant women who tested positive for syphilis, and 470 (92%) potential congenital syphilis were averted. One hundred nine pregnant women tested positive for syphilis in the third trimester, and 85 (78%) had babies without congenital syphilis. During their pregnancy, 85 (12%) women tested negative at least once, and 55 (65%) had babies with congenital syphilis. Thirty-nine women had no reported syphilis screening 30 days or longer before delivery. CONCLUSIONS: Screening for syphilis both early and in the third trimester prevented many pregnant women with syphilis from having a baby with congenital syphilis. Preventing all congenital syphilis would likely require preventing all syphilis among women.

Down-regulation of tricarboxylic acid (TCA) cycle genes blocks progression through the first mitotic division in Caenorhabditis elegans embryos.

The cell cycle is a highly regulated process that enables the accurate transmission of chromosomes to daughter cells. Here we uncover a previously unknown link between the tricarboxylic acid (TCA) cycle and cell cycle progression in the Caenorhabditis elegans early embryo. We found that down-regulation of TCA cycle components, including citrate synthase, malate dehydrogenase, and aconitase, resulted in a one-cell stage arrest before entry into mitosis: pronuclear meeting occurred normally, but nuclear envelope breakdown, centrosome separation, and chromosome condensation did not take place. Mitotic entry is controlled by the cyclin B-cyclin-dependent kinase 1 (Cdk1) complex, and the inhibitory phosphorylation of Cdk1 must be removed in order for the complex to be active. We found that following down-regulation of the TCA cycle, cyclin B levels were normal but CDK-1 remained inhibitory-phosphorylated in one-cell stage-arrested embryos, indicative of a G2-like arrest. Moreover, this was not due to an indirect effect caused by checkpoint activation by DNA damage or replication defects. These observations suggest that CDK-1 activation in the C. elegans one-cell embryo is sensitive to the metabolic state of the cell, and that down-regulation of the TCA cycle prevents the removal of CDK-1 inhibitory phosphorylation. The TCA cycle was previously shown to be necessary for the development of the early embryo in mammals, but the molecular processes affected were not known. Our study demonstrates a link between the TCA cycle and a specific cell cycle transition in the one-cell stage embryo.

A Low-Cost Partner Notification Strategy for the Control of Sexually Transmitted Diseases: A Case Study From Louisiana.

OBJECTIVES: We estimated the costs and effectiveness of implementing a partner notification (PN) strategy for highly prevalent sexually transmitted diseases (STDs) within the Louisiana STD/HIV Program. METHODS: We carried out a telephone-based PN approach on an experimental basis in 2 public STD clinics in Louisiana from June 2010 to May 2012. We monitored data on the resources used for identifying, tracing, treating, and managing the infected cases and their partners to estimate the intervention costs. RESULTS: Our results indicated that implementation of telephone-based PN should not increase the STD control program's expenses by more than 4.5%. This low-cost PN approach could successfully identify and treat 1 additional infected case at a cost of only $171. We found that the cost per disability-adjusted life year averted (a health outcome measure), because of the adoption of selective screening with partner tracing, was $4499. This was significantly lower than the gross domestic product per capita of the United States, a threshold used for defining highly cost-effective health interventions. CONCLUSIONS: Adoption of PN for gonorrhea and chlamydia should be considered a national strategy for prevention and control of these diseases.

Redox Zonation and Oscillation in the Hyporheic Zone of the Ganges-Brahmaputra-Meghna Delta: Implications for the Fate of Groundwater Arsenic during Discharge.

Riverbank sediment cores and pore waters, shallow well waters, seepage waters and river waters were collected along the Meghna Riverbank in Gazaria Upazila, Bangladesh in Jan. 2006 and Oct.-Nov. 2007 to investigate hydrogeochemical processes controlling the fate of groundwater As during discharge. Redox transition zones from suboxic (0-2 m depth) to reducing (2-5 m depth) then suboxic conditions (5-7 m depth) exist at sites with sandy surficial deposits, as evidenced by depth profiles of pore water (n=7) and sediment (n=11; diffuse reflectance, Fe(III)/Fe ratios and Fe(III) concentrations). The sediment As enrichment zone (up to ~700 mg kg-1) is associated with the suboxic zones mostly between 0-2 m depth and less frequently between 5-7 m depth. The As enriched zones consist of several 5 to 10 cm-thick dispersed layers and span a length of ~5-15 m horizontally from the river shore. Depth profiles of riverbank pore water deployed along a 32 m transect perpendicular to the river shore show elevated levels of dissolved Fe (11.6±11.7 mg L-1) and As (118±91 µg L-1, mostly as arsenite) between 2-5 m depth, but lower concentrations between 0-2 m depth (0.13±0.19 mg L-1 Fe, 1±1 µg L-1 As) and between 5-6 m depth (1.14±0.45 mg L-1 Fe, 28±17 µg L-1 As). Because it would take more than a few hundred years of steady groundwater discharge (~10 m yr-1) to accumulate hundreds of mg kg-1 of As in the riverbank sediment, it is concluded that groundwater As must have been naturally elevated prior to anthropogenic pumping of the aquifer since the 1970s. Not only does this lend unequivocal support to the argument that As occurrence in the Ganges-Brahmaputra-Meghna Delta groundwater is of geogenic origin, it also calls attention to the fate of this As enriched sediment as it may recycle As into the aquifer.

Cysteine and resistance to oxidative stress: implications for virulence and antibiotic resistance.

Reactive oxygen species (ROS), including the superoxide radical anion (O2•-), hydrogen peroxide (H2O2), and the hydroxyl radical (•HO), are inherent components of bacterial metabolism in an aerobic environment. Bacteria also encounter exogenous ROS, such as those produced by the host cells during the respiratory burst. As ROS have the capacity to damage bacterial DNA, proteins, and lipids, detoxification of ROS is critical for bacterial survival. It has been recently recognised that low-molecular-weight (LMW) thiols play a central role in this process. Here, we review the emerging role of cysteine in bacterial resistance to ROS with a link to broader elements of bacterial lifestyle closely associated with cysteine-mediated oxidative stress response, including virulence and antibiotic resistance.

Pal power: Demonstration of the functional association of the Helicobacter pylori flagellar motor with peptidoglycan-associated lipoprotein (Pal) and its preliminary crystallographic analysis.

The bacterial flagellar motor is a molecular nanomachine, the assembly and regulation of which requires many accessory proteins. Their identity, structure and function are often discovered through characterisation of mutants with impaired motility. Here, we demonstrate the functional association of the Helicobacter pylori peptidoglycan-associated lipoprotein (HpPal) with the flagellar motor by analysing the motility phenotype of the ∆pal mutant, and present the results of the preliminary X-ray crystallographic analysis of its globular C-terminal domain HpPal-C. Purified HpPal-C behaved as a dimer in solution. Crystals of HpPal-C were grown by the hanging drop vapour diffusion method using medium molecular weight polyethylene glycol (PEG) Smear as the precipitating agent. The crystals belong to the primitive orthorhombic space group P1 with unit cell parameters a = 50.7, b = 63.0, c = 75.1 Å. X-ray diffraction data were collected to 1.8 Å resolution on the Australian Synchrotron beamline MX2. Calculation of the Matthews coefficient (VM=2.24 Å3/Da) and molecular replacement showed that the asymmetric unit contains two protein subunits. This study is an important step towards elucidation of the non-canonical role of H. pylori Pal in the regulation, or function of, the flagellar motor.

Determination of Protein-Ligand Binding Affinities by Thermal Shift Assay.

Quantification of protein-ligand interactions is crucial for understanding the protein's biological function and for drug discovery. In this study, we employed three distinct approaches for determination of protein-ligand binding affinities by a thermal shift assay using a single ligand concentration. We present the results of the comparison of the performance of the conventional curve fitting (CF) method and two newly introduced methods - assuming zero heat capacity change across small temperature ranges (ZHC) and utilizing the unfolding equilibrium constant (UEC); the latter has the advantage of reducing calculations by obtaining the unfolding equilibrium constant directly from the experimental data. Our results highlight superior performance of the ZHC and UEC methods over the conventional CF method in estimating the binding affinity, irrespective of the ligand concentration. In addition, we evaluated how the new methods can be applied to high-throughput screening for potential binders, when the enthalpy (ΔH L) and molar heat capacity change (ΔC PL) of ligand binding are unknown. Our results suggest that, in this scenario, using the -300 cal K-1 mol-1 assumption for ΔC pL and either -5 kcal mol-1 or the average enthalpy efficiency-based estimation for ΔH L(T) can still provide reasonable estimates of the binding affinity. Incorporating the new methods into the workflow for screening of small drug-like molecules, typically conducted using single-concentration libraries, could greatly simplify and streamline the drug discovery process.

O-glycosylation of intrinsically disordered regions regulates homeostasis of membrane proteins in streptococci.

Proteins harboring intrinsically disordered regions (IDRs) lacking stable secondary or tertiary structures are abundant across the three domains of life. These regions have not been systematically studied in prokaryotes. Our genome-wide analysis identifies extracytoplasmic serine/threonine-rich IDRs in several biologically important membrane proteins in streptococci. We demonstrate that these IDRs are O-glycosylated with glucose by glycosyltransferases GtrB and PgtC2 in Streptococcus pyogenes and Streptococcus pneumoniae, and with N-acetylgalactosamine by a Pgf-dependent mechanism in Streptococcus mutans. Absence of glycosylation leads to a defect in biofilm formation under ethanol-stressed conditions in S. mutans. We link this phenotype to the C-terminal IDR of a post-translocation secretion chaperone PrsA. O-glycosylation of the IDR protects this region from proteolytic degradation. The IDR length attenuates the efficiency of glycosylation and, consequently, the expression level of PrsA. Taken together, our data reveal that O-glycosylation of IDRs functions as a dynamic switch of protein homeostasis in streptococci.