Staphylococcal nuclease is an enzyme with enormous catalytic power, accelerating phosphodiester bond hydrolysis by a factor of 10 16 over the spontaneous rate. The mechanistic basis for this rate acceleration was investigated by substitution of the active site residues Glu 43 , Arg 35 , and Arg 87 with unnatural amino acid analogs. Two Glu 43 mutants, one containing the nitro analog of glutamate and the other containing homoglutamate, retained high catalytic activity at pH 9.9, but were less active than the wild-type enzyme at lower pH values. The x-ray crystal structure of the homoglutamate mutant revealed that the carboxylate side chain of this residue occupies a position and orientation similar to that of Glu 43 in the wild-type enzyme. The increase in steric bulk is accommodated by a backbone shift and altered torsion angles. The nitro and the homoglutamate mutants display similar pH versus rate profiles, which differ from that of the wild-type enzyme. Taken together, these studies suggest that Glu 43 may not act as a general base, as previously thought, but may play a more complex structural role during catalysis.
Electronic medical records of patients evaluated in the Ophthalmic Genetics clinic at the National Eye Institute (NEI) between 2008 and 2018 were searched for a superficial ODD diagnosis. Color fundus and autofluorescence images were reviewed to confirm ODD, supplemented with optical coherence tomography (OCT) in uncertain cases when available. Demographic information, examination, and genetic testing were reviewed. Disc areas and disc-to-macula distance to disc diameter ratios (DM : DD) were calculated.Fifty six of 6207 patients had photographically confirmed ODD (0.9%). Drusen were predominantly bilateral (66%), with a female (62%) and Caucasian (73%) predilection. ODD prevalence in our cohort of patients with inherited retinal degenerations was 2.5%, and ODD were more prevalent in the rod-cone dystrophy subgroup at 2.95% (OR = 3.3 [2.1-5.3], P < 0.001) compared to the ophthalmic genetics cohort. Usher patients were more likely to have ODD (10/132, 7.6%, OR = 9.0 [4.3-17.7], P < 0.001) and had significantly smaller discs compared to the rest of our ODD cohort (disc area: P=0.001, DM : DD: P=0.03). Discussion. While an association between ODD and retinitis pigmentosa has been reported, this study surveys a large cohort of patients with inherited eye conditions and finds the prevalence of superficial ODD is lower than that in the literature. Some subpopulations, such as rod-cone dystrophy and Usher syndrome, had a higher prevalence than the cohort as a whole.
Abstract Background Bacteroides fragilis and Bacteroides thetaiotaomicron are members of the normal human intestinal microbiota. However, both organisms are capable of causing opportunistic infections, during which the environmental conditions to which the bacteria are exposed change dramatically. To further explore their potential for contributing to infection, we have characterized the expression in B. thetaiotaomicron of four homologues of the gene encoding the C10 cysteine protease SpeB, a potent extracellular virulence factor produced by Streptococcus pyogenes . Results We identified a paralogous set of genes ( btp genes) in the B. thetaiotaomicron genome, that were related to C10 protease genes we recently identified in B. fragilis . Similar to C10 proteases found in B. fragilis, three of the B. thetaiotaomicron homologues were transcriptionally coupled to genes encoding small proteins that are similar in structural architecture to Staphostatins, protease inhibitors associated with Staphopains in Staphylococcus aureus . The expression of genes for these C10 proteases in both B. fragilis and B. thetaiotaomicron was found to be regulated by environmental stimuli, in particular by exposure to oxygen, which may be important for their contribution to the development of opportunistic infections. Conclusions Genes encoding C10 proteases are increasingly identified in operons which also contain genes encoding proteins homologous to protease inhibitors. The Bacteroides C10 protease gene expression levels are responsive to different environmental stimuli suggesting they may have distinct roles in the bacterial-host interaction.
Summary The tumor suppressor BRCA1 encodes multiple protein products including the canonical BRCA1-p220 (p220), which plays important roles in repair of diverse types of DNA damage. However, contributions of other BRCA1 -encoded protein isoforms to DNA damage repair are less clear. Here, we report that the BRCA1-IRIS (IRIS) isoform has critical functions in the Fanconi anemia (FA) pathway and in repair of DNA interstrand crosslinks (ICLs). Loss of IRIS expression sensitizes cells to ICLs and impairs ICL repair. ICL formation stimulates association of IRIS with both FANCD2 and the FA core complex, which promotes FANCD2 recruitment to damage sites. The unique, BRCA1 intron 11-encoded C-terminal tail of IRIS is required for complex formation with FANCD2 and for ICL-inducible FANCD2 mono-ubiquitylation. Collectively, our findings reveal that IRIS plays an essential role, upstream of the p220-directed HR, in the FA pathway through a previously unrecognized mechanism that depends on the IRIS-FANCA-FANCD2 interaction. Highlights BRCA1 splicing isoform BRCA1-IRIS is required for interstrand crosslink (ICL) repair. BRCA1-IRIS interacts with FANCD2 and promotes its recruitment to sites of ICL damage. BRCA1-IRIS, but not BRCA1-p220, promotes ICL-inducible FANCD2 mono-ubiquitylation. The unique C-terminal tail of BRCA1-IRIS is essential for its function in ICL repair.
Among the Gram-positive anaerobic bacteria associated with clinical infections, the Gram-positive anaerobic cocci (GPAC) are the most prominent and account for approximately 25-30% of all isolated anaerobic bacteria from clinical specimens. Still, routine culture and identification of these slowly growing anaerobes to the species level has been limited in the diagnostic laboratory, mainly due to the requirement of prolonged incubation times and time-consuming phenotypic identification. In addition, GPAC are mostly isolated from polymicrobial infections with known pathogens and therefore their relevance has often been overlooked. However, through improvements in diagnostic and in particular molecular techniques, the isolation and identification of individual genera and species of GPAC associated with specific infections have been enhanced. Furthermore, the taxonomy of GPAC has undergone considerable changes over the years, mainly due to the development of molecular identification methods. Existing species have been renamed and novel species have been added, resulting in changes of the nomenclature. As the abundance and significance of GPAC in clinical infections grow, knowledge of virulence factors and antibiotic resistance patterns of different species becomes more important. The present review describes recent advances of GPAC and what is known of the biology and pathogenic effects of Anaerococcus, Finegoldia, Parvimonas, Peptoniphilus and Peptostreptococcus, the most important GPAC genera isolated from human infections.
Significance Spontaneous overexpression of endogenous IRIS, an alternatively spliced product of the tumor suppressor gene BRCA1 , allows it to function as an oncoprotein that stimulates a potentially lethal outcome, i.e. metastasis of human cancer cells to tissues served, in part, by the arterial circulation. It does so by suppressing phosphatase and tensin homolog (PTEN) mRNA synthesis, thereby stabilizing and activating HIF-1α in normoxic cells. Thus, this study provides a strong rationale for exploring the therapeutic value of interfering with spontaneously overexpressed IRIS function in multiple types of tumors that can naturally overexpress it.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLinear Free Energy Analysis of Hydrogen Bonding in ProteinsJon S. Thorson, Eli Chapman, Elizabeth C. Murphy, Peter G. Schultz, and J. Kevin JudiceCite this: J. Am. Chem. Soc. 1995, 117, 3, 1157–1158Publication Date (Print):January 1, 1995Publication History Published online1 May 2002Published inissue 1 January 1995https://pubs.acs.org/doi/10.1021/ja00108a044https://doi.org/10.1021/ja00108a044research-articleACS PublicationsRequest reuse permissionsArticle Views473Altmetric-Citations45LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Many bacterial pathogens interfere with the contact system (kallikrein-kinin system) in human plasma. Activation of this system has two consequences: cleavage of high-molecular-mass kininogen (HK) resulting in release of the potent proinflammatory peptide bradykinin, and initiation of the intrinsic pathway of coagulation. In this study, two species of the Gram-negative anaerobic commensal organism Bacteroides, namely Bacteroides fragilis and Bacteroides thetaiotaomicron, were found to bind HK and fibrinogen, the major clotting protein, from human plasma as shown by immunoelectron microscopy and Western blot analysis. In addition, these Bacteroides species were capable of activating the contact system at its surface leading to a significant prolongation of the intrinsic coagulation time and also to the release of bradykinin. Members of the genus Bacteroides have been known to act as opportunistic pathogens outside the gut, with B. fragilis being the most common isolate from clinical infections, such as intra-abdominal abscesses and bacteraemia. The present results thus provide more insight into how Bacteroides species cause infection.
