Structure and activity of ChiX: a peptidoglycan hydrolase required for chitinase secretion by Serratia marcescens.
Structure and activity of ChiX: a peptidoglycan hydrolase required for chitinase secretion by Serratia marcescens.
复制标题
CHIX的结构和活性：甲状酸酯Marcescens分支酶分泌所需的肽聚糖水解酶。
DOI：
10.1042/bcj20170633
复制
发表时间：
2018-01-23
期刊：
影响因子：
--
通讯作者：
Sargent F
中科院分区：
文献类型：
--
作者：
Owen RA;Fyfe PK;Lodge A;Biboy J;Vollmer W;Hunter WN;Sargent F
革兰氏阴性细菌粘质沙雷氏菌分泌许多参与胞外几丁质降解的蛋白质。这种所谓的几丁质分解机制包括三种类型的几丁质酶和一种溶解性多糖单加氧酶。在S. marcescens，chiWXYZ，其被认为参与几丁质分解机制的分泌。遗传学证据指出ChiX蛋白是分泌机制中的关键参与者，因为在S. marcescens导致一种突变株，其几丁质分解机制的所有成员的分泌都被阻断。在这项工作中，ChiX的详细结构和生化特性。ChiX的高分辨率晶体结构揭示了该蛋白质是肽酶LAS家族的成员。ChiX被证明是一种含锌的金属酶，并且体外测定证明ChiX是一种切割细菌肽聚糖中的交联的l-Ala d-Glu内肽酶。这种催化活性被证明与几丁质分解机制的分泌密切相关，因为ChiX Asp-120残基的取代导致了一种变体蛋白，该蛋白既不能消化肽聚糖，也不能拯救ChiX突变株的表型。
The Gram-negative bacterium Serratia marcescens secretes many proteins that are involved in extracellular chitin degradation. This so-called chitinolytic machinery includes three types of chitinase enzymes and a lytic polysaccharide monooxygenase. An operon has been identified in S. marcescens, chiWXYZ, that is thought to be involved in the secretion of the chitinolytic machinery. Genetic evidence points to the ChiX protein being a key player in the secretion mechanism, since deletion of the chiX gene in S. marcescens led to a mutant strain blocked for secretion of all members of the chitinolytic machinery. In this work, a detailed structural and biochemical characterisation of ChiX is presented. The high-resolution crystal structure of ChiX reveals the protein to be a member of the LAS family of peptidases. ChiX is shown to be a zinc-containing metalloenzyme, and in vitro assays demonstrate that ChiX is an l-Ala d-Glu endopeptidase that cleaves the cross-links in bacterial peptidoglycan. This catalytic activity is shown to be intimately linked with the secretion of the chitinolytic machinery, since substitution of the ChiX Asp-120 residue results in a variant protein that is both unable to digest peptidoglycan and cannot rescue the phenoytype of a chiX mutant strain.