The Structure of the Staphylococcus aureus Sortase-Substrate Complex Reveals How the Universally Conserved LPXTG Sorting Signal Is Recognized
The Structure of the Staphylococcus aureus Sortase-Substrate Complex Reveals How the Universally Conserved LPXTG Sorting Signal Is Recognized
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DOI：
10.1074/jbc.m109.022624
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发表时间：
2009-09-04
影响因子：
4.8
通讯作者：
Clubb, Robert T.
中科院分区：
文献类型：
--
作者：
Suree, Nuttee;Liew, Chu Kong;Clubb, Robert T.
在革兰氏阳性细菌中，分选酶在细胞壁包膜中组装表面蛋白和菌毛。分选酶催化转肽化反应，将其多肽底物内高度保守的LPXTG分选信号连接到细胞壁或其他毛蛋白亚基。转肽酶和分选信号识别的分子基础尚不清楚，因为催化的中间体寿命很短。我们通过合成LPXTG信号的类似物来克服这个问题，该信号与酶的稳定共价配合物模拟了一个关键的硫酰基催化中间体。本文报道了其与金黄色葡萄球菌SrtA分选酶共价复合物的溶液结构和动力学。与先前报道的晶体结构形成鲜明对比的是，我们发现SrtA通过关闭和固定活性位点环自适应地识别LPXTG分选信号。我们还使用化学位移定位实验来定位脂质II的甘油三酯部分的结合位点，脂质II是表面蛋白附着的第二个底物。我们提出了一个统一的转肽化反应模型来解释关键活性位点残基的功能。由于sortase催化的锚定反应是许多细菌病原体的毒力所必需的，因此本文提出的结果可能有助于开发新的抗感染药物。
In Gram-positive bacteria, sortase enzymes assemble surface proteins and pili in the cell wall envelope. Sortases catalyze a transpeptidation reaction that joins a highly conserved LPXTG sorting signal within their polypeptide substrate to the cell wall or to other pilin subunits. The molecular basis of transpeptidation and sorting signal recognition are not well understood, because the intermediates of catalysis are short lived. We have overcome this problem by synthesizing an analog of the LPXTG signal whose stable covalent complex with the enzyme mimics a key thioacyl catalytic intermediate. Here we report the solution structure and dynamics of its covalent complex with the Staphylococcus aureus SrtA sortase. In marked contrast to a previously reported crystal structure, we show that SrtA adaptively recognizes the LPXTG sorting signal by closing and immobilizing an active site loop. We have also used chemical shift mapping experiments to localize the binding site for the triglycine portion of lipid II, the second substrate to which surface proteins are attached. We propose a unified model of the transpeptidation reaction that explains the functions of key active site residues. Since the sortase-catalyzed anchoring reaction is required for the virulence of a number of bacterial pathogens, the results presented here may facilitate the development of new anti-infective agents.