%0 Journal Article
%T PpiD is a player in the network of periplasmic chaperones in Escherichia coli
%A Yvonne Matern
%A Birgitta Barion
%A Susanne Behrens-Kneip
%J BMC Microbiology
%D 2010
%I BioMed Central
%R 10.1186/1471-2180-10-251
%X The analysis of the effects of both deletion and overexpression of ppiD on cell envelope phenotypes revealed that PpiD in contrast to prior observations plays only a minor role, if any, in the maturation of OMPs and cannot compensate for the lack of SurA in the periplasm. On the other hand, our results show that overproduction of PpiD rescues a surA skp double mutant from lethality. In the presence of increased PpiD levels surA skp cells show reduced activities of both the SigmaE-dependent and the Cpx envelope stress responses, and contain increased amounts of folded species of the major OMP OmpA. These effects require the anchoring of PpiD in the inner membrane but are independent of its parvulin-like PPIase domain. Moreover, a PpiD protein lacking the PPIase domain also complements the growth defects of an fkpA ppiD surA triple PPIase mutant and exhibits chaperone activity in vitro. In addition, PpiD appears to collaborate with DegP, as deletion of ppiD confers a temperature-dependent conditional synthetic phenotype in a degP mutant.This study provides first direct evidence that PpiD functions as a chaperone and contributes to the network of periplasmic chaperone activities without being specifically involved in OMP maturation. Consistent with previous work, our data support a model in which the chaperone function of PpiD is used to aid in the early periplasmic folding of many newly translocated proteins.It is well established that numerous chaperones, folding catalysts and proteases exist in the periplasm of E. coli and cooperate in protein folding and protein quality control in this cellular compartment of the cell. At least three of these factors, SurA, Skp and DegP, assist in the maturation of integral ¦Â-barrel outer membrane proteins (OMPs), a major class of proteins in the E. coli outer membrane, and are thought to be responsible for the transport of OMP folding intermediates through the periplasm to the OMP assembly site, a multi-protein complex in the oute
%U http://www.biomedcentral.com/1471-2180/10/251