Crystal structures reveal a thiol protease-like catalytic triad in the C-terminal region of Pasteurella multocida toxin
Crystal structures reveal a thiol protease-like catalytic triad in the C-terminal region of Pasteurella multocida toxin
复制标题
DOI：
10.1073/pnas.0608197104
复制
发表时间：
2007-03-20
影响因子：
11.1
通讯作者：
Horiguchi, Yasuhiko
中科院分区：
文献类型：
--
作者：
Kitadokoro, Kengo;Kamitani, Shigeki;Horiguchi, Yasuhiko
多杀性巴氏杆菌毒素(PMT)是该细菌产生的毒力因子之一，它通过上调异源三聚体GT-Pase GQ和G12/13下游的各种信号级联来发挥其毒性作用。在这里，我们介绍了PMT的C-末端区域(残基575-1,285)的晶体结构，它携带着细胞内的活性部分。PMT C-末端区域的整体结构呈特洛伊木马状，由三个结构域组成，从N端到C端分别命名为C1、C2和C3，具有“脚”-“体”和“头”型排列。C1区在空间结构上与艰难梭菌毒素B的N端结构域有显著的相似性，它将毒素分子引向质膜。C3结构域具有Cys-HisAsp催化三联体，只有当Cys从二硫键释放时才有组织。三联体的立体排列与木瓜酶或其他携带Cys-His-Asp的酶的立体排列很好地对应。当构成三联体的氨基酸之一发生突变时，PMT对靶细胞的毒性完全被消除。我们的结果表明，PMT是一种携带半胱氨酸蛋白酶样催化三联体的酶毒素，依赖于靶细胞质膜的氧化还原状态和功能。
Pasteurella multocida toxin (PMT), one of the virulence factors produced by the bacteria, exerts its toxicity by up-regulating various signaling cascades downstream of the heterotrimeric GT-Pases Gq and G12/13 in an unknown fashion. Here, we present the crystal structure of the C-terminal region (residues 575-1,285) of PMT, which carries an intracellularly active moiety. The overall structure of C-terminal region of PMT displays a Trojan horse-like shape, composed of three domains with a "feet" - "body"-, and "head"-type arrangement, which were designated C1, C2, and C3 from the N to the C terminus, respectively. The C1 domain,showing marked similarity in steric structure to the N-terminal domain of Clostridium difficile toxin B, was found to lead the toxin molecule to the plasma membrane. The C3 domain possesses the Cys-HisAsp catalytic triad that is organized only when the Cys is released from a disulfide bond. The steric alignment of the triad corresponded well to that of papain or other enzymes carrying Cys-His-Asp. PMT toxicities on target cells were completely abrogated when one of the amino acids constituting the triad was mutated. Our results indicate that PMT is an enzyme toxin carrying the cysteine protease-like catalytic triad dependent on the redox state and functions on the cytoplasmic face of the plasma membrane of target cells.