Staphylococcus aureus Sortase A (SrtA) is an important Gram-positive membrane enzyme which catalyzes the anchoring of many cell surface proteins conserved with the LPXTG sequence. Recently SrtA has been demonstrated to be a dimer with a Kd of 55 microM in vitro. Herein, we show that a single point mutation of amino acid residue on the surface of SrtA can completely disrupt the dimerization. Native polyacrylamide gel electrophoresis and analytical gel filtration chromatography were used to detect the dimer-monomer equilibrium of SrtA mutants. Circular dichroism spectrum experiments were performed to study the conformational change of each SrtA mutant. An enzyme activity assay confirmed that all the SrtA mutants were active in vitro. Our results not only are important for understanding the SrtA protein self-associating mechanism but also provided the necessary starting materials for the study of sortase A pathway in vivo, which may have significant implications for discovering microbial physiology and give a potential target for novel Gram-positive antibiotics.
BackgroundAs one of the top three high tuberculosis (TB) burden countries, China is a country where the overall TB incidence continues to decline. However, due to its large population and area, the increased TB burden exists in regional areas.MethodsThis retrospective study analyzed local inpatient pulmonary TB cases in the Affiliated Hospital of Zunyi Medical University (AHZMU) from January 2016 to December 2018 in a high TB incidence and economically-less-developed area of China. Four methods, acid-fast bacilli stain, culture, Xpert and LAMP, were used to detect Mycobacterium tuberculosis (M.tb), while proportional method and Xpert were used to identify rifampicin-resistant TB (RR-TB). Case number, treatment history, M.tb confirmed TB and rifampicin resistant proportion were analyzed to investigate the local TB epidemic.ResultsTotal 3,910 local inpatient cases with pulmonary TB were admitted to AHZMU during this study period. The annual numbers of total TB cases increased 26.4% (from 1,173 to 1,483), while new cases increased 29.6% (from 936 to 1,213) and RR-TB cases increased 2.7 times (from 31 to 84). Meanwhile, the percentage of previously treated cases declined from 20.2 to 18.2% and the M.tb confirmed TB proportion increased from 34.7 to 49.7%.ConclusionThe elevated M.tb confirmed TB proportion and the declined percentage of previously treated cases indicated the improved TB diagnosis and treatment of AHZMU. However, the increasing number of total TB cases, new and RR-TB cases showed an upward trend and increased TB burden in a relatively underdeveloped area of China.
The electrographic (E.G.) camera is one of the most powerful modern detectors having high sensitivity, extended spectral response, extreme spatial resolution, low background, no threshold, good linearity and large dynamic image. A combination of highly uniform electric and magnetic fields produces distortion-free and extremely sharp images which are recorded by electron sensitive emulsions (Figure 1).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.