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MxiD, an outer membrane protein necessary for the secretion of the Shigella flexneri Ipa invasins
Author(s) -
Allaoui Abdelmounaaïm,
Sansonetti Philippe J.,
Parsot Claude
Publication year - 1993
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.1365-2958.1993.tb01097.x
Subject(s) - shigella flexneri , biology , secretion , bacterial outer membrane , shigella , microbiology and biotechnology , biochemistry , escherichia coli , gene
Summary The invasive phenotype of Shigella flexneri is conferred by a 220 kb virulence plasmid, pWR100, that encodes both the Ipa proteins, which are involved in the entry process, and factors which are required for the export and correct localization of the Ipa proteins. We have characterized the mxiD gene, whose expression, like that of the ipa operon, is regulated by temperature. After inactivation of mxiD , the mutant strain was unable to invade HeLa cells and to provoke keratoconjunctivitis in guinea‐pigs. Analysis of culture supernatants indicated that wild‐type S. flexneri secretes about nine polypeptides and that secretion of several of these, including IpaA, IpaB, and IpaC, is abolished in the mxiD mutant. Examination of the membrane proteins of the wild‐type and mxiD strains suggested that MxiD is an outer membrane protein. Amino acid sequence comparison revealed that MxiD is homologous to the YscC protein of Yersinia enterocolitica and to the C ‐terminal region of the PulD protein of Klebsiella pneumoniae. Both YscC and PulD are involved in extracellular protein secretion. These results indicate that MxiD is an essential component of the Ipa secretion apparatus.