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Cell Rep. 2012 Jun 28;1(6):656-64. doi: 10.1016/j.celrep.2012.05.016. Epub 2012 May 31.

Structure of a peptidoglycan amidase effector targeted to Gram-negative bacteria by the type VI secretion system.

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  • 1Department of Microbiology, University of Washington, Seattle, WA 98195, USA.

Abstract

The target range of a bacterial secretion system can be defined by effector substrate specificity or by the efficacy of effector delivery. Here, we report the crystal structure of Tse1, a type VI secretion (T6S) bacteriolytic amidase effector from Pseudomonas aeruginosa. Consistent with its role as a toxin, Tse1 has a more accessible active site than related housekeeping enzymes. The activity of Tse1 against isolated peptidoglycan shows its capacity to act broadly against Gram-negative bacteria and even certain Gram-positive species. Studies with intact cells indicate that Gram-positive bacteria can remain vulnerable to Tse1 despite cell wall modifications. However, interbacterial competition studies demonstrate that Tse1-dependent lysis is restricted to Gram-negative targets. We propose that the previously observed specificity for T6S against Gram-negative bacteria is a consequence of high local effector concentration achieved by T6S-dependent targeting to its site of action rather than inherent effector substrate specificity.

Copyright © 2012 The Authors. Published by Elsevier Inc. All rights reserved.

PMID:
22813741
[PubMed - indexed for MEDLINE]
PMCID:
PMC3401384
Free PMC Article

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