Chan Albert H, Yi Sung Wook, Terwilliger Austen L, Maresso Anthony W, Jung Michael E, Clubb Robert T
From the Department of Chemistry and Biochemistry, UCLA-DOE Institute of Genomics and Proteomics, and the Molecular Biology Institute, University of California, Los Angeles, California 90095 and.
From the Department of Chemistry and Biochemistry.
J Biol Chem. 2015 Oct 16;290(42):25461-74. doi: 10.1074/jbc.M115.670984. Epub 2015 Aug 31.
The endospore forming bacterium Bacillus anthracis causes lethal anthrax disease in humans and animals. The ability of this pathogen to replicate within macrophages is dependent upon the display of bacterial surface proteins attached to the cell wall by the B. anthracis Sortase A ((Ba)SrtA) enzyme. Previously, we discovered that the class A (Ba)SrtA sortase contains a unique N-terminal appendage that wraps around the body of the protein to contact the active site of the enzyme. To gain insight into its function, we determined the NMR structure of (Ba)SrtA bound to a LPXTG sorting signal analog. The structure, combined with dynamics, kinetics, and whole cell protein display data suggest that the N terminus modulates substrate access to the enzyme. We propose that it may increase the efficiency of protein display by reducing the unproductive hydrolytic cleavage of enzyme-protein covalent intermediates that form during the cell wall anchoring reaction. Notably, a key active site loop (β7/β8 loop) undergoes a disordered to ordered transition upon binding the sorting signal, potentially facilitating recognition of lipid II.
形成芽孢的细菌炭疽芽孢杆菌可在人和动物中引发致命的炭疽病。这种病原体在巨噬细胞内复制的能力取决于炭疽芽孢杆菌分选酶A（(Ba)SrtA）将附着于细胞壁的细菌表面蛋白展示出来。此前，我们发现A类（Ba）SrtA分选酶含有一个独特的N端附属结构，该结构环绕蛋白质主体以接触酶的活性位点。为深入了解其功能，我们确定了与LPXTG分选信号类似物结合的（Ba）SrtA的核磁共振结构。该结构结合动力学、动力学和全细胞蛋白展示数据表明，N端调节底物与酶的接触。我们提出，它可能通过减少在细胞壁锚定反应过程中形成的酶-蛋白共价中间体的非生产性水解切割来提高蛋白展示效率。值得注意的是，一个关键的活性位点环（β7/β8环）在结合分选信号后会发生从无序到有序的转变，这可能有助于对脂质II的识别。
