Structure of a Peptidoglycan Amidase Effector Targeted to Gram-Negative Bacteria by the Type VI Secretion System

Seemay Chou, Nhat Khai Bui, Alistair B. Russell, Katrina W. Lexa, Taylor E. Gardiner, Michele LeRoux, Waldemar Vollmer, Joseph D. Mougous
2012 Cell Reports  
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
more » ... 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 Gramnegative 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.
doi:10.1016/j.celrep.2012.05.016 pmid:22813741 pmcid:PMC3401384 fatcat:pvtqvyo4pbhubdj72lwp2mpuvm