The D3 Bacteriophage alpha-Polymerase Inhibitor (Iap) Peptide Disrupts O-Antigen Biosynthesis through Mimicry of the Chain Length Regulator Wzz in Pseudomonas aeruginosa

作者：Taylor Veronique L; Udaskin Molly L; Islam Salim T; Lam Joseph S^*

来源：Journal of Bacteriology, 2013, 195(20): 4735-4741.

DOI：10.1128/JB.00903-13

Lysogenic bacteriophage D3 causes seroconversion of Pseudomonas aeruginosa PAO1 from serotype O5 to O16 by inverting the linkage between O-specific antigen (OSA) repeat units from alpha to beta. The OSA units are polymerized by Wzy to modal lengths regulated by Wzz(1) and Wzz(2). A key component of the D3 seroconversion machinery is the inhibitor of alpha-polymerase (Iap) peptide, which is able to solely suppress alpha-linked long-chain OSA production in P. aeruginosa PAO1. To establish the target specificity of Iap for Wzy(alpha), changes in OSA phenotypes were examined via Western immunoblotting for wzz(1) and wzz(2) single-knockout strains, as well as a wzz(1) wzz(2) double knockout, following the expression of iap from a tuneable vector. Increased induction of Iap expression completely abrogated OSA production in the wzz(1) wzz(2) double mutant, while background levels of OSA production were still observed in either of the single mutants. Therefore, Iap inhibition of OSA biosynthesis was most effective in the absence of both Wzz proteins. Sequence alignment analyses revealed a high degree of similarity between Iap and the first transmembrane segment (TMS) of either Wzz(1) or Wzz(2). Various topology prediction analyses of the Iap sequence consistently predicted the presence of a single TMS, suggesting a propensity for Iap to insert itself into the inner membrane (IM). The compromised ability of Iap to abrogate Wzy(alpha) function in the presence of Wzz(1) or Wzz(2) provides compelling evidence that inhibition occurs after Wzy(alpha) inserts itself into the IM and is achieved through mimicry of the first TMS from the Wzz proteins of P. aeruginosa PAO1.

• 出版日期2013-10