5OQ1 image
Entry Detail
PDB ID:
5OQ1
Keywords:
Title:
Crystal structure of Serratia marcescens ChiX (used as MR model for superior PDB 5OPZ)
Biological Source:
Source Organism:
PDB Version:
Deposition Date:
2017-08-10
Release Date:
2018-01-17
Method Details:
Experimental Method:
Resolution:
1.34 Å
R-Value Free:
0.16
R-Value Work:
0.13
R-Value Observed:
0.13
Space Group:
P 1 21 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:ChiX
Chain IDs:A, B
Chain Length:137
Number of Molecules:2
Biological Source:Serratia marcescens
Primary Citation
Structure and activity of ChiX: a peptidoglycan hydrolase required for chitinase secretion by Serratia marcescens.
Biochem. J. 475 415 428 (2018)
PMID: 29229757 DOI: 10.1042/BCJ20170633

Abstact

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.

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