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Salmonella InvG forms a ring‐like multimer that requires the InvH lipoprotein for outer membrane localization
Author(s) -
Crago Aimee M.,
Koronakis Vassilis
Publication year - 1998
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 - 10.1046/j.1365-2958.1998.01036.x
Subject(s) - bacterial outer membrane , biology , secretion , effector , cytoplasm , virulence , type three secretion system , microbiology and biotechnology , escherichia coli , salmonella , membrane protein , inner membrane , membrane , biochemistry , bacteria , gene , genetics
Salmonella species translocate virulence effector proteins from the bacterial cytoplasm into mammalian host cells by means of a type III secretion apparatus, encoded by the pathogenicity island‐1 (SPI‐1). Little is known about the assembly and structure of this secretion apparatus, but the InvG protein is essential and could be an outer membrane secretion channel for the effector proteins. We observed that in recombinant Escherichia coli , the yield of InvG was enhanced by co‐expression of InvH, and showed that mutation of invH decreased the level of InvG in wild‐type Salmonella typhimurium . In E. coli , InvG alone was able to form an SDS‐resistant multimer, but InvG localization to the outer membrane was dependent upon InvH, a lipoprotein itself located in the outer membrane, and no other SPI‐1 specific protein. InvG targeted to the outer membrane by InvH became accessible to extracellular protease. InvG and InvH did not, however, appear to form a stable complex. Electron microscopy of InvG membrane protein purified from E. coli revealed that it forms an oligomeric ring‐like structure with inner and outer diameters, 7 nm and 15 nm respectively.