Extracellular association and cytoplasmic partitioning of the IpaB and IpaC invasins of S. flexneri.
Shigella species cause bacillary dysentery in humans by invading colonic epithelial cells. IpaB and IpaC, two major invasins of these pathogens, are secreted into the extracellular milieu. We show here that IpaB and IpaC form a complex in the extracellular medium and that each binds independently to a 17 kDa polypeptide, IpgC, in the bacterial cytoplasm. The IpgC polypeptide was found to be necessary for bacterial entry into epithelial cells, to stabilize the otherwise unstable IpaB protein, and to prevent the proteolytic degradation of IpaC that occurs through its association with unprotected IpaB. We propose that IpgC, which is not secreted and thus acts as a molecular chaperone, serves as a receptor that prevents premature oligomerization of IpaB and IpaC within the cytoplasm of Shigella cells.
Unité de Pathogénie Microbienne Moléculaire, Paris, France.
R
R
Ménard
P
P
Sansonetti
C
C
Parsot
T
T
Vasselon
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D002451:Cell Compartmentation; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism*; D004847:Epithelial Cells; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics; D011485:Protein Binding; D012763:Shigella flexneri / Q000378:metabolism / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics / Q000502:physiology
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; C053476:invasin, Yersinia; C087447:ipaB protein, Shigella