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A Genome-Scale Proteomic Screen Identifies a Role for DnaK in Chaperoning of Polar Autotransporters in Shigella
Author(s) -
Anuradha Janakiraman,
Kathryn R. Fixen,
Andrew N. Gray,
Hironori Niki,
Marcia B. Goldberg
Publication year - 2009
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.00833-09
Subject(s) - ftsz , biology , shigella flexneri , cytoplasm , bacterial outer membrane , microbiology and biotechnology , green fluorescent protein , secretion , chaperone (clinical) , escherichia coli , genetics , biochemistry , gene , medicine , pathology
Autotransporters are outer membrane proteins that are widely distributed among gram-negative bacteria. Like other autotransporters, theShigella autotransporter IcsA, which is required for actin assembly during infection, is secreted at the bacterial pole. In the bacterial cytoplasm, IcsA localizes to poles and potential cell division sites independent of the cell division protein FtsZ. To identify bacterial proteins involved in the targeting of IcsA to the pole in the bacterial cytoplasm, we screened a genome-scale library ofE scherichia coli proteins tagged with green fluorescent protein (GFP) for those that displayed a localization pattern similar to that of IcsA-GFP in cells that lack functional FtsZ using a strain carrying a temperature-sensitiveftsZ allele. For each protein that mimicked the localization of IcsA-GFP, we tested whether IcsA localization was dependent on the presence of the protein. Although these approaches did not identify a polar receptor for IcsA, the cytoplasmic chaperone DnaK both mimicked IcsA localization at elevated temperatures as a GFP fusion and was required for the localization of IcsA to the pole in the cytoplasm ofE. coli . DnaK was also required for IcsA secretion at the pole inS higella flexneri . The localization of DnaK-GFP to poles and potential cell division sites was dependent on elevated growth temperature and independent of the presence of IcsA or functional FtsZ; native DnaK was found to be enhanced at midcell and the poles. A secondShigella autotransporter, SepA, also required DnaK for secretion, consistent with a role of DnaK more generally in the chaperoning of autotransporter proteins in the bacterial cytoplasm.

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