Zoll Sebastian, Schlag Martin, Shkumatov Alexander V, Rautenberg Maren, Svergun Dmitri I, Götz Friedrich, Stehle Thilo
Interfaculty Institute of Biochemistry, University of Tuebingen, Tuebingen, Germany.
J Bacteriol. 2012 Aug;194(15):3789-802. doi: 10.1128/JB.00331-12. Epub 2012 May 18.
The bifunctional major autolysin Atl plays a key role in staphylococcal cell separation. Processing of Atl yields catalytically active amidase (AM) and glucosaminidase (GL) domains that are each fused to repeating units. The two repeats of AM (R1 and R2) target the enzyme to the septum, where it cleaves murein between dividing cells. We have determined the crystal structure of R2, which reveals that each repeat folds into two half-open β-barrel subunits. We further demonstrate that lipoteichoic acid serves as a receptor for the repeats and that this interaction depends on conserved surfaces in each subunit. Small-angle X-ray scattering of the mature amidase reveals the presence of flexible linkers separating the AM, R1, and R2 units. Different levels of flexibility for each linker provide mechanistic insights into the conformational dynamics of the full-length protein and the roles of its components in cell wall association and catalysis. Our analysis supports a model in which the repeats direct the catalytic AM domain to the septum, where it can optimally perform the final step of cell division.
双功能主要自溶素Atl在葡萄球菌细胞分裂中起关键作用。Atl的加工产生具有催化活性的酰胺酶（AM）和氨基葡萄糖苷酶（GL）结构域，它们各自与重复单元融合。AM的两个重复序列（R1和R2）将该酶靶向隔膜，在那里它切割分裂细胞之间的胞壁质。我们已经确定了R2的晶体结构，该结构表明每个重复序列折叠成两个半开放的β-桶亚基。我们进一步证明脂磷壁酸作为重复序列的受体，并且这种相互作用取决于每个亚基中的保守表面。成熟酰胺酶的小角X射线散射揭示了分隔AM、R1和R2单元的柔性接头的存在。每个接头不同程度的柔性为全长蛋白质的构象动力学及其组分在细胞壁结合和催化中的作用提供了机制上的见解。我们的分析支持一种模型，其中重复序列将催化性AM结构域导向隔膜，在那里它可以最佳地执行细胞分裂的最后一步。
