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A novel DnaJ‐like protein in Escherichia coli inserts into the cytoplasmic membrane with a Type III topology
Author(s) -
Clarke David J.,
Jacq A.,
Holland I. B.
Publication year - 1996
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1996.tb02646.x
Subject(s) - biology , periplasmic space , ftsz , chaperone (clinical) , transmembrane domain , cell envelope , mutant , membrane topology , transmembrane protein , membrane protein , cytoplasm , microbiology and biotechnology , inner membrane , escherichia coli , bacterial outer membrane , signal peptide , peptide sequence , biochemistry , membrane , gene , medicine , receptor , pathology
Summary We describe a novel Escherichia coli protein, DjlA, containing a highly conserved J‐region motif, which is present in the DnaJ protein chaperone family and required for interaction with DnaK. Remarkably, DjlA is shown to be a membrane protein, localized to the inner membrane with the unusual Type III topology (N‐out, C‐in). Thus, DjlA appears to present an extremely short N‐terminus to the periplasm and has a single transmembrane domain (TMD) and a large cytoplasmic domain containing the C‐terminal J‐region. Analysis of the TMD of DjIA and recently identified homologues in Coxiella burnetti and Haemophilus influenzae revealed a striking pattern of conserved glycines (or rarely alanine), with a four‐residue spacing. This motif, predicted to form a spiral groove in the TMD, is more marked than a repeating glycine motif, implicated in the dimerization of TMDs of some eukaryotic proteins. This feature of DjlA could represent a promiscuous docking mechanism for interaction with a variety of membrane proteins. DjlA null mutants can be isolated but these appear rapidly to accumulate suppressors to correct envelope and growth defects. Moderate (10‐fold) overproduction of DjlA suppresses a mutation in FtsZ but markedly perturbs cell division and cell‐envelope growth in minimal medium. We propose that DjlA plays a role in the correct assembly, activity and/or maintenance of a number of membrane proteins, including two‐component signal‐transduction systems.