Title

VirK Is a Periplasmic Protein Required for Efficient Secretion of Plasmid-Encoded Toxin from Enteroaggregative Escherichia coli

Authors

Authors

G. Tapia-Pastrana; L. Chavez-Duenas; H. Lanz-Mendoza; K. Teter;F. Navarro-Garcia

Comments

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Abbreviated Journal Title

Infect. Immun.

Keywords

OUTER-MEMBRANE PROTEINS; GRAM-NEGATIVE BACTERIA; SHIGELLA-FLEXNERI; PASSENGER DOMAIN; EPITHELIAL-CELLS; BINDING DOMAIN; CHAPERONE SKP; AUTOTRANSPORTER; PET; SURFACE; Immunology; Infectious Diseases

Abstract

Despite the autotransporter (AT) moniker, AT secretion appears to involve the function of periplasmic chaperones. We identified four periplasmic proteins that specifically bound to plasmid-encoded toxin (Pet), an AT produced by enteroaggregative Escherichia coli (EAEC). These proteins include the 17-kDa Skp chaperone and the 37-kDa VirK protein. We found that the virK gene is present in different Enterobacteriaceae. VirK bound to misfolded conformations of the Pet passenger domain, but it did not bind to the folded passenger domain or to the beta domain of Pet. Assays with an EAEC Delta virK mutant and its complemented version showed that, in the absence of VirK, Pet was not secreted but was instead retained in the periplasm as proteolytic fragments. In contrast, Pet was secreted from a Delta skp mutant. VirK was not required for the insertion of porin proteins into the outer membrane but assisted with insertion of the Pet beta domain into the outer membrane. Loss of VirK function blocked the EAEC-mediated cytotoxic effect against HEp-2 cells. Thus, VirK facilitates the secretion of the AT Pet by maintaining the passenger domain in a conformation that both avoids periplasmic proteolysis and facilitates beta-domain insertion into the outer membrane.

Journal Title

Infection and Immunity

Volume

80

Issue/Number

7

Publication Date

1-1-2012

Document Type

Article

Language

English

First Page

2276

Last Page

2285

WOS Identifier

WOS:000305599400003

ISSN

0019-9567

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