Striated preferentially expressed gene deficiency leads to mitochondrial dysfunction in developing cardiomyocytes.

A deficiency of striated preferentially expressed gene (Speg), a member of the myosin light chain kinase family, results in abnormal myofibril structure and function of immature cardiomyocytes (CMs), corresponding with a dilated cardiomyopathy, heart failure and perinatal death. Mitochondrial development plays a role in cardiomyocyte maturation. Therefore, this study investigated whether Speg deficiency ( - / - ) in CMs would result in mitochondrial abnormalities. Speg wild-type and Speg-/- C57BL/6 littermate mice were utilized for assessment of mitochondrial structure by transmission electron and confocal microscopies. Speg was expressed in the first and second heart fields at embryonic (E) day 7.5, prior to the expression of mitochondrial Na+/Ca2+/Li+ exchanger (NCLX) at E8.5. Decreases in NCLX expression (E11.5) and the mitochondrial-to-nuclear DNA ratio (E13.5) were observed in Speg-/- hearts. Imaging of E18.5 Speg-/- hearts revealed abnormal mitochondrial cristae, corresponding with decreased ATP production in cells fed glucose or palmitate, increased levels of mitochondrial superoxide and depolarization of mitochondrial membrane potential. Interestingly, phosphorylated (p) PGC-1α, a key mediator of mitochondrial development, was significantly reduced in Speg-/- hearts during screening for targeted genes. Besides Z-line expression, Speg partially co-localized with PGC-1α in the sarcomeric region and was found in the same complex by co-immunoprecipitation. Overexpression of a Speg internal serine/threonine kinase domain in Speg-/- CMs promoted translocation of pPGC-1α into the nucleus, and restored ATP production that was abolished by siRNA-mediated silencing of PGC-1α. Our results demonstrate a critical role of Speg in mitochondrial development and energy metabolism in CMs, mediated in part by phosphorylation of PGC-1α.

Dilated-Left Ventricular Non-Compaction Cardiomyopathy in a Pediatric Case with SPEG Compound Heterozygous Variants.

Left Ventricular Non-Compaction (LVNC) is defined by the triad prominent myocardial trabecular meshwork, thin compacted layer, and deep intertrabecular recesses. LVNC associated with dilation is characterized by the coexistence of left ventricular dilation and systolic dysfunction. Pediatric cases with dilated-LVNC have worse outcomes than those with isolated dilated cardiomyopathy and adult patients. Herein, we report a clinical and genetic investigation using trio-based whole-exome sequencing of a pediatric case with early-onset dilated-LVNC. Compound heterozygous mutations were identified in the Striated Muscle Enriched Protein Kinase (SPEG) gene, a key regulator of cardiac calcium homeostasis. A paternally inherited mutation: SPEG; p.(Arg2470Ser) and the second variant, SPEG; p.(Pro2687Thr), is common and occurred de novo. Subsequently, Sanger sequencing was performed for the family in order to segregate the variants. Thus, the index case, his father, and both sisters carried the SPEG: p.(Arg2470Ser) variant. Only the index patient carried both SPEG variants. Both sisters, as well as the patient's father, showed LVNC without cardiac dysfunction. The unaffected mother did not harbor any of the variants. The in silico analysis of the identified variants (rare and common) showed a decrease in protein stability with alterations of the physical properties as well as high conservation scores for the mutated residues. Interestingly, using the Project HOPE tool, the SPEG; p.(Pro2687Thr) variant is predicted to disturb the second fibronectin type III domain of the protein and may abolish its function. To our knowledge, the present case is the first description of compound heterozygous SPEG mutations involving a de novo variant and causing dilated-LVNC without neuropathy or centronuclear myopathy.

Free spermidine evokes superoxide radicals that manifest toxicity.

Spermidine and other polyamines alleviate oxidative stress, yet excess spermidine seems toxic to Escherichia coli unless it is neutralized by SpeG, an enzyme for the spermidine N-acetyl transferase function. Thus, wild-type E. coli can tolerate applied exogenous spermidine stress, but ΔspeG strain of E. coli fails to do that. Here, using different reactive oxygen species (ROS) probes and performing electron paramagnetic resonance spectroscopy, we provide evidence that although spermidine mitigates oxidative stress by lowering overall ROS levels, excess of it simultaneously triggers the production of superoxide radicals, thereby causing toxicity in the ΔspeG strain. Furthermore, performing microarray experiment and other biochemical assays, we show that the spermidine-induced superoxide anions affected redox balance and iron homeostasis. Finally, we demonstrate that while RNA-bound spermidine inhibits iron oxidation, free spermidine interacts and oxidizes the iron to evoke superoxide radicals directly. Therefore, we propose that the spermidine-induced superoxide generation is one of the major causes of spermidine toxicity in E. coli.

Characterization of a novel zebrafish model of SPEG-related centronuclear myopathy.

Centronuclear myopathy (CNM) is a congenital neuromuscular disorder caused by pathogenic variation in genes associated with membrane trafficking and excitation-contraction coupling (ECC). Bi-allelic autosomal-recessive mutations in striated muscle enriched protein kinase (SPEG) account for a subset of CNM patients. Previous research has been limited by the perinatal lethality of constitutive Speg knockout mice. Thus, the precise biological role of SPEG in developing skeletal muscle remains unknown. To address this issue, we generated zebrafish spega, spegb and spega;spegb (speg-DKO) mutant lines. We demonstrated that speg-DKO zebrafish faithfully recapitulate multiple phenotypes associated with CNM, including disruption of the ECC machinery, dysregulation of calcium homeostasis during ECC and impairment of muscle performance. Taking advantage of zebrafish models of multiple CNM genetic subtypes, we compared novel and known disease markers in speg-DKO with mtm1-KO and DNM2-S619L transgenic zebrafish. We observed Desmin accumulation common to all CNM subtypes, and Dnm2 upregulation in muscle of both speg-DKO and mtm1-KO zebrafish. In all, we establish a new model of SPEG-related CNM, and identify abnormalities in this model suitable for defining disease pathomechanisms and evaluating potential therapies. This article has an associated First Person interview with the joint first authors of the paper.

Antibiotic susceptibility of Bacillus velezensis.

We evaluated the antibiotic minimum inhibitory concentrations (MICs) of 123 Bacillus velezensis strains predominantly isolated from fermented soybean foods from Korea. When the 2018 European Food Safety Authority breakpoint values for Bacillus spp. were applied, all the strains were sensitive to chloramphenicol, clindamycin, erythromycin, gentamicin, kanamycin, tetracycline and vancomycin, and eight strains (6.5%) were resistant to streptomycin. The population distribution in MIC tests with streptomycin was continuous and the profile was clearly different from that expected for acquired antibiotic resistance. As of 25 October 2021, there were 181 complete published genomes of B. velezensis strains; 175 (96.7%) and 136 (75.2%) of these strains, respectively, possess potential tetracycline and streptomycin resistance genes tetL and ant(6) in the chromosome. In Bacillus licheniformis, SpeG confers resistance to clindamycin and there is an 'speG' gene annotated in the genomes of 180 B. velezensis strains; however, the gene products exhibit ≤26.6% amino acid identity with that from B. licheniformis DSM 13T. All the potential antibiotic resistance genes in the 181 B. velezensis strains were intrinsic, and traits of lateral gene transfer were not found. In this context, B. velezensis may not present a high risk in terms of antibiotic resistance in food fermentation or human use.

High-fiber-diet-related metabolites improve neurodegenerative symptoms in patients with obesity with diabetes mellitus by modulating the hippocampal-hypothalamic endocrine axis.

Objective: Through transcriptomic and metabolomic analyses, this study examined the role of high-fiber diet in obesity complicated by diabetes and neurodegenerative symptoms. Method: The expression matrix of high-fiber-diet-related metabolites, blood methylation profile associated with pre-symptomatic dementia in elderly patients with type 2 diabetes mellitus (T2DM), and high-throughput single-cell sequencing data of hippocampal samples from patients with Alzheimer's disease (AD) were retrieved from the Gene Expression Omnibus (GEO) database and through a literature search. Data were analyzed using principal component analysis (PCA) after quality control and data filtering to identify different cell clusters and candidate markers. A protein-protein interaction network was mapped using the STRING database. To further investigate the interaction among high-fiber-diet-related metabolites, methylation-related DEGs related to T2DM, and single-cell marker genes related to AD, AutoDock was used for semi-flexible molecular docking. Result: Based on GEO database data and previous studies, 24 marker genes associated with high-fiber diet, T2DM, and AD were identified. Top 10 core genes include SYNE1, ANK2, SPEG, PDZD2, KALRN, PTPRM, PTPRK, BIN1, DOCK9, and NPNT, and their functions are primarily related to autophagy. According to molecular docking analysis, acetamidobenzoic acid, the most substantially altered metabolic marker associated with a high-fiber diet, had the strongest binding affinity for SPEG. Conclusion: By targeting the SPEG protein in the hippocampus, acetamidobenzoic acid, a metabolite associated with high-fiber diet, may improve diabetic and neurodegenerative diseases in obese people.

Genetic screening for hypertension and COVID-19 reveals functional variation of SPEG potentially associated with severe COVID-19 in women.

The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to more than 6.4 million deaths worldwide. The prevalent comorbidity between hypertension and severe COVID-19 suggests common genetic factors may affect the outcome of both diseases. As both hypertension and severe COVID-19 demonstrate sex-biased prevalence, common genetic factors between the two diseases may display sex-biased differential associations. By evaluating COVID-19 association signals of 172-candidate hypertension single nucleotide polymorphisms (SNPs) derived from more than 1 million European individuals in two sex-stratified severe COVID-19 genome-wide association studies from UK BioBank with European ancestry, we revealed one functional cis expression quantitative trait locus of SPEG (rs12474050) showing sex-biased association with severe COVID-19 in women. The risk allele rs12474050*T associates with higher blood pressure. In our study, we found it is significantly correlated with lower SPEG expression in muscle-skeletal but with higher expression in both brain cerebellum and cerebellar hemisphere. Additionally, nominal significances were detected for the association between rs12474050*T and lower SPEG expression in both heart left ventricle and atrial appendage; among these tissues, the SPEG expression is nominally significantly higher in females than in males. Further analysis revealed SPEG is mainly expressed in cardiomyocytes in heart and is upregulated upon SARS-CoV-2 infection, with significantly higher upregulation of SPEG only observed in female but not in male COVID-19 patients compared to both normal female and male individuals, suggesting upregulation of SPEG is a female-specific protective mechanism against COVID-19 induced heart damage. Taken together, our analyses suggest the involvement of SPEG in both hypertension and severe COVID-19 in women, which provides new insights for sex-biased effect of severe COVID-19 in women.

A Novel SPEG mutation causing congenital myopathy with fiber size disproportion and dilated cardiomyopathy with heart transplantation.

Congenital myopathies are a heterogeneous group of conditions diagnosed based on the clinical presentation, muscle histopathology and genetic defects. Recessive mutations in the SPEG gene have been described in recent years and are primarily associated with centronuclear myopathy with cardiomyopathy. In this report, we describe two Brazilian siblings, aged 13 and 6 years, with a novel homozygous mutation (c.8872 C>T:p.Arg2958Ter) in the SPEG gene leading to a congenital myopathy. In the older sibling, the muscle biopsy showed fiber size disproportion. The mean diameter of type 2 fibers (119 µm) was significantly higher than type 1 (57 µm) (P < 0,001) with a 72% prevalence of type 1 fibers. The patient also had progressive cardiomyopathy treated with heart transplantation. The present report expands the muscle histopathological findings related to mutations in the SPEG gene, including fiber size disproportion without central nuclei. Additionally, this report describes the first case of heart transplantation in a patient with SPEG mutations.

Mild congenital myopathy due to a novel variation in SPEG gene.

Centronuclear myopathies (CNMs) are a subgroup of congenital myopathies (CMs) characterized by muscle weakness, genetic heterogeneity, and predominant type 1 fibers and increased central nuclei in muscle biopsy. Mutations in CNM-causing genes such as MTM1, DNM2, BIN1, RYR1, CACNA1S, TTN, and extraordinary rarely SPEG (striated muscle preferentially expressed protein kinase) have been identified for about 60-80% of patients. Herein, we report a case of CM due to a novel variation in the SPEG gene, manifested by mild neonatal hypotonia, muscle weakness, delayed motor milestones, and ophthalmoplegia, without dilated cardiomyopathy. We identified a novel variation [c.153C>T (p.Asn51=) in exon 1] in the SPEG gene with whole-exome sequencing and confirmed by Sanger sequencing. Mild intellectual disability has not been associated with SPEG-related CM in the previous reports. We suggest that this report expands the phenotypic spectrum of SPEG-related CM, and further case reports are required to expand the genotype-phenotype correlations.

Mass Spectrometry-Based Glycoproteomics and Prostate Cancer.

Aberrant glycosylation has long been known to be associated with cancer, since it is involved in key mechanisms such as tumour onset, development and progression. This review will focus on protein glycosylation studies in cells, tissue, urine and serum in the context of prostate cancer. A dedicated section will cover the glycoforms of prostate specific antigen, the molecule that, despite some important limitations, is routinely tested for helping prostate cancer diagnosis. Our aim is to provide readers with an overview of mass spectrometry-based glycoproteomics of prostate cancer. From this perspective, the first part of this review will illustrate the main strategies for glycopeptide enrichment and mass spectrometric analysis. The molecular information obtained by glycoproteomic analysis performed by mass spectrometry has led to new insights into the mechanism linking aberrant glycosylation to cancer cell proliferation, migration and immunoescape.

Criticality of a conserved tyrosine residue in the SpeG protein from Escherichia coli.

The SpeG spermidine/spermine N-acetyltransferase (SSAT) from Escherichia coli belongs to the Gcn5-related N-acetyltransferase (GNAT) superfamily of proteins. In vitro characterization of this enzyme shows it acetylates the polyamines spermine and spermidine, with a preference toward spermine. This enzyme has a conserved tyrosine residue (Y135) that is found in all SSAT proteins and many GNAT functional subfamilies. It is located near acetyl coenzyme A in the active center of these proteins and has been suggested to act as a general acid in a general acid/base chemical mechanism. In contrast, a previous study showed this residue was not critical for E. coli SpeG enzymatic activity when mutated to phenylalanine. This result was quite different from previous studies with a comparable residue in the human and mouse SSAT proteins, which also acetylate spermine and spermidine. Therefore, we constructed several mutants of the E. coli SpeG Y135 residue and tested their enzymatic activity. We found this conserved residue was indeed critical for E. coli SpeG enzyme activity and may behave similarly in other SSAT proteins.

Clinical and genetic analysis of a case with centronuclear myopathy caused by SPEG gene mutation: a case report and literature review.

BACKGROUND: Centronuclear myopathy (CNM), a subtype of congenital myopathy (CM), is a group of clinical and genetically heterogeneous muscle disorders. Since the discovery of the SPEG gene and disease-causing variants, only a few additional patients have been reported. CASE PRESENTATION: The child, a 13-year-old female, had delayed motor development since childhood, weakness of both lower extremities for 10 years, gait swinging, and a positive Gower sign. Her distal muscle strength of both lower extremities was grade IV. The electromyography showed myogenic damage and electromyographic changes. Her 11-year-old sister had a similar muscle weakness phenotype. Gene sequencing revealed that both sisters had SPEG compound heterozygous mutations, and the mutation sites were c.3715 + 4C > T and c.3588delC, which were derived from their parents. These variant sites have not been reported before. The muscle biopsy showed the nucleic (> 20% of fibers) were located in the center of the cell, the average diameter of type I myofibers was slightly smaller than that of type II myofibers, and the pathology of type I myofibers was dominant, which agreed with the pathological changes of centronuclear myopathy. CONCLUSIONS: The clinical phenotypes of CNM patients caused by mutations at different sites of the SPEG gene are also different. In this case, there was no cardiomyopathy. This study expanded the number of CNM cases and the mutation spectrum of the SPEG gene to provide references for prenatal diagnosis and genetic counseling.

Exploring Obscurin and SPEG Kinase Biology.

Three members of the obscurin protein family that contain tandem kinase domains with important signaling functions for cardiac and striated muscles are the giant protein obscurin, its obscurin-associated kinase splice isoform, and the striated muscle enriched protein kinase (SPEG). While there is increasing evidence for the specific roles that each individual kinase domain plays in cross-striated muscles, their biology and regulation remains enigmatic. Our present study focuses on kinase domain 1 and the adjacent low sequence complexity inter-kinase domain linker in obscurin and SPEG. Using Phos-tag gels, we show that the linker in obscurin contains several phosphorylation sites, while the same region in SPEG remained unphosphorylated. Our homology modeling, mutational analysis and molecular docking demonstrate that kinase 1 in obscurin harbors all key amino acids important for its catalytic function and that actions of this domain result in autophosphorylation of the protein. Our bioinformatics analyses also assign a list of putative substrates for kinase domain 1 in obscurin and SPEG, based on the known and our newly proposed phosphorylation sites in muscle proteins, including obscurin itself.

Mechanisms underlying pathological Ca2+ handling in diseases of the heart.

Cardiomyocyte contraction relies on precisely regulated intracellular Ca2+ signaling through various Ca2+ channels and transporters. In this article, we will review the physiological regulation of Ca2+ handling and its role in maintaining normal cardiac rhythm and contractility. We discuss how inherited variants or acquired defects in Ca2+ channel subunits contribute to the development or progression of diseases of the heart. Moreover, we highlight recent insights into the role of protein phosphatase subunits and striated muscle preferentially expressed protein kinase (SPEG) in atrial fibrillation, heart failure, and cardiomyopathies. Finally, this review summarizes current drug therapies and new advances in genome editing as therapeutic strategies for the cardiac diseases caused by aberrant intracellular Ca2+ signaling.

Clonal diversity of methicillin-resistant Staphylococcus aureus (MRSA) from bloodstream infections in northern Japan: Identification of spermidine N-acetyltransferase gene (speG) in staphylococcal cassette chromosomes (SCCs) associated with type II and IV SCCmec.

OBJECTIVES: Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of bloodstream infections (BSIs). We aimed to study molecular epidemiological characteristics of MRSA isolates from BSIs in northern Japan to elucidate the recent trend of their clonal diversity. METHODS: MRSA isolates (n = 277) were collected from blood samples of patients who attended healthcare facilities in Hokkaido, the northern main island of Japan, for a two-year period from August 2017. Genotypes, virulence factors/drug-resistance determinants, and structure of SCCmec complex were analysed by PCR and sequencing analysis. RESULTS: SCCmec-IIa (n = 171, 61.7%) with coagulase genotype (coa-) II, ST5/ST764/ST2389 was the most common genetic trait, followed by SCCmec-IVa (n = 78, 28.2%), and IVl (n = 10, 3.6%). Among the MRSA-IVa, 14 isolates (5.1% of all the isolates) had genetic features identical to USA300 clone (ST8/coa-IIIa/spa-t008 having ΦSa2USA and ACME-I), while PVL/ACME-negative MRSA-IVa isolates (n = 64) were classified into coa-IIa/IIIa/VIIa/VIIb, with coa-VIIa/spa-t1784/ST1 being dominant. Other minor clones included ST8-SCCmec-I, and ST30/ST45/ST81/ST121/ST1232-SCCmec-V, among which the ST1232 isolate harboured PVL genes. Spermidine N-acetyltransferase gene (speG), which is typically present in ACME-I of USA300 clone, was also identified in two isolates, ACME-II'-positive ST764-MRSA-IIa and ACME-negative ST1-MRSA-IVa, showing resistance to spermine. speG of these isolates was located in additional SCCs adjacent to SCCmec. CONCLUSIONS: Our present study revealed clonal diversity of MRSA from BSIs in Japan, with increased prevalence of ST8-USA300. Distinct types of speG-carrying SCCs associated with SCCmec-II or IV were identified.

Double the trouble: giant proteins with dual kinase activity in the heart.

Obscurin and its homolog, striated muscle preferentially expressed gene (SPEG), constitute a unique group of proteins abundantly expressed in striated muscles that contain two tandemly arranged MLCK-like kinases. The physiological significance of the dual kinase motifs is largely understudied; however, a collection of recent studies characterizing their binding interactions, putative targets, and disease-linked mutations have begun to shed light on their potential roles in muscle pathophysiology. Specifically, obscurin kinase 1 is proposed to regulate cardiomyocyte adhesion via phosphorylating N-cadherin, whereas SPEG kinases 1 and 2 regulate Ca2+ cycling by phosphorylating junctophilin-2 and the sarcoendoplasmic Ca2+ ATPase 2 (SERCA2). Herein, we review what is currently known regarding the potential substrates, physiological roles, and disease associations of obscurin and SPEG tandem kinase domains and provide future directions that have yet to be investigated.

Loss of SPEG Inhibitory Phosphorylation of Ryanodine Receptor Type-2 Promotes Atrial Fibrillation.

BACKGROUND: Enhanced diastolic calcium (Ca2+) release through ryanodine receptor type-2 (RyR2) has been implicated in atrial fibrillation (AF) promotion. Diastolic sarcoplasmic reticulum Ca2+ leak is caused by increased RyR2 phosphorylation by PKA (protein kinase A) or CaMKII (Ca2+/calmodulin-dependent kinase-II) phosphorylation, or less dephosphorylation by protein phosphatases. However, considerable controversy remains regarding the molecular mechanisms underlying altered RyR2 function in AF. We thus aimed to determine the role of SPEG (striated muscle preferentially expressed protein kinase), a novel regulator of RyR2 phosphorylation, in AF pathogenesis. METHODS: Western blotting was performed with right atrial biopsies from patients with paroxysmal AF. SPEG atrial knockout mice were generated using adeno-associated virus 9. In mice, AF inducibility was determined using intracardiac programmed electric stimulation, and diastolic Ca2+ leak in atrial cardiomyocytes was assessed using confocal Ca2+ imaging. Phosphoproteomics studies and Western blotting were used to measure RyR2 phosphorylation. To test the effects of RyR2-S2367 phosphorylation, knockin mice with an inactivated S2367 phosphorylation site (S2367A) and a constitutively activated S2367 residue (S2367D) were generated by using CRISPR-Cas9. RESULTS: Western blotting revealed decreased SPEG protein levels in atrial biopsies from patients with paroxysmal AF in comparison with patients in sinus rhythm. SPEG atrial-specific knockout mice exhibited increased susceptibility to pacing-induced AF by programmed electric stimulation and enhanced Ca2+ spark frequency in atrial cardiomyocytes with Ca2+ imaging, establishing a causal role for decreased SPEG in AF pathogenesis. Phosphoproteomics in hearts from SPEG cardiomyocyte knockout mice identified RyR2-S2367 as a novel kinase substrate of SPEG. Western blotting demonstrated that RyR2-S2367 phosphorylation was also decreased in patients with paroxysmal AF. RyR2-S2367A mice exhibited an increased susceptibility to pacing-induced AF, and aberrant atrial sarcoplasmic reticulum Ca2+ leak, as well. In contrast, RyR2-S2367D mice were resistant to pacing-induced AF. CONCLUSIONS: Unlike other kinases (PKA, CaMKII) that increase RyR2 activity, SPEG phosphorylation reduces RyR2-mediated sarcoplasmic reticulum Ca2+ release. Reduced SPEG levels and RyR2-S2367 phosphorylation typified patients with paroxysmal AF. Studies in S2367 knockin mouse models showed a causal relationship between reduced S2367 phosphorylation and AF susceptibility. Thus, modulating SPEG activity and phosphorylation levels of the novel S2367 site on RyR2 may represent a novel target for AF treatment.

SpeG polyamine acetyltransferase enzyme from Bacillus thuringiensis forms a dodecameric structure and exhibits high catalytic efficiency.

Polyamines are important for regulating biofilms and the exopolysaccharide of the biofilm matrix of Bacillus subtilis. Understanding how enzymes can regulate polyamine concentrations is critical for learning more about how these processes occur in diverse bacteria. Here, we describe the structure and function of another member of the spermidine/spermine acetyltransferases (SSAT) found in Bacilli. The SpeG enzyme from B. thuringiensis (BtSpeG) binds polyamines in its allosteric site and adopts a dodecameric oligomeric state similar to other SpeG enzymes from Gram-negative bacteria. Our kinetic results show the catalytic efficiency of BtSpeG was greater than any previously characterized SpeG to date, and in contrast to other SpeG proteins it exhibited very similar kinetic properties toward both spermine and spermidine. Similar to the SpeG enzyme from E. coli, BtSpeG was able to acetylate spermidine on the N1 and N8 positions. The turnover of BtSpeG toward spermine and spermidine was also two to three orders of magnitude greater than any other Bacilli SSAT enzyme that has been previously characterized. SpeG proteins from Bacilli, including B. cereus, B. thuringiensis and B. anthracis share nearly identical sequences and therefore our results likely provide insight into the structure/function relationship across multiple Bacillus species.

Novel SPEG variant cause centronuclear myopathy in China.

BACKGROUND: Centronuclear myopathy (CNM), a subtype of congenital myopathy (CM), is a group of clinical and genetically heterogeneous muscle disorders. Centronuclear myopathy is a kind of disease difficult to diagnose due to its genetic diversity. Since the discovery of the SPEG gene and disease-causing variants, only a few additional patients have been reported. METHODS: A radiograph test, ultrasonic test, and biochemical tests were applied to clinical diagnosis of CNM. We performed trio medical exome sequencing of the family and conservation analysis to identify variants. RESULTS: We report a pair of severe CNM twins with the same novel homozygous SPEG variant c. 8710A>G (p.Thr2904Ala) identified by clinical trio medical exome sequencing of the family and conservation analysis. The twins showed clinical symptoms of facial weakness, hypotonia, arthrogryposis, strephenopodia, patent ductus arteriosus, and pulmonary arterial hypertension. CONCLUSIONS: Our report expands the clinical and molecular repertoire of CNM and enriches the variant spectrum of the SPEG gene in the Chinese population and helps us further understand the pathogenesis of CNM.

Analysis of crystalline and solution states of ligand-free spermidine N-acetyltransferase (SpeG) from Escherichia coli.

Spermidine N-acetyltransferase (SpeG) transfers an acetyl group from acetyl-coenzyme A to an N-terminal amino group of intracellular spermidine. This acetylation inactivates spermidine, reducing the polyamine toxicity that tends to occur under certain chemical and physical stresses. The structure of the SpeG protein from Vibrio cholerae has been characterized: while the monomer possesses a structural fold similar to those of other Gcn5-related N-acetyltransferase superfamily members, its dodecameric structure remains exceptional. In this paper, structural analyses of SpeG isolated from Escherichia coli are described. Like V. cholerae SpeG, E. coli SpeG forms dodecamers, as revealed by two crystal structures of the ligand-free E. coli SpeG dodecamer determined at 1.75 and 2.9 Šresolution. Although both V. cholerae SpeG and E. coli SpeG can adopt an asymmetric open dodecameric state, solution analysis showed that the oligomeric composition of ligand-free E. coli SpeG differs from that of ligand-free V. cholerae SpeG. Based on these data, it is proposed that the equilibrium balance of SpeG oligomers in the absence of ligands differs from one species to another and thus might be important for SpeG function.