Biophysical and biochemical characterization of proteins involved in a-glucan biosynthesis in mycobacteria

[摘要] A capsule composed of mainly α-glucan forms the most outermost layer of cell envelope of Mycobacterium tuberculosis, the causing agent of tuberculosis. Capsule participates in modulating the immune system responses. In GlgE pathway, one of the three pathways involved in α-glucan synthesis, trehalose in converted to glucan through the activity of four enzymes, trehalose synthase, maltokinase Pep2, maltosyltransferase GlgE and branching enzyme GlgB. It has shown that M. tuberculosis TreS and Pep2 form an octameric complex together. During this study we solved the structure of the complex at 3.6 Å in M. smegmatis. The structure reveals two pairs of Pep2 monomers bind to the opposite sides of the diamond shaped TreS tetramer in a 4 + 4 complex. However, studying the stoichiometry of the complex using other techniques such as: ITC, AUC and SAXS indicates a 4 + 2 complex formation in the solution. Moreover, our data using size exclusion chromatography would suggest that this complex formation is pH dependent and favors complex formation at more acidic pHs. This study is a step forward towards better understanding of the capsule synthesis in M. tuberculosis and highlights the role of complex formation between enzymes as an effective strategy to control the metabolic pathways in mycobacteria.

[发布机构] University:University of Birmingham;Department:School of Biosciences

[关键词] Q Science;QR Microbiology