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J. Bacteriol., 10 1997, 6264-6270, Vol 179, No. 20
J Hwang, X Zhong and PC Tai
The antibacterial peptide toxin colicin V uses a dedicated signal
sequence-independent system for its secretion in Escherichia coli and
requires the products of three genes, cvaA, cvaB, and tolC. As a member of
the membrane fusion protein family, CvaA is supposed to form a bridge that
connects the inner and outer membranes via interaction with CvaB and TolC,
respectively. In this study, we investigated the possible interaction of
these proteins. When CvaA or CvaB was absent, the corresponding amount of
CvaB or CvaA, respectively, was decreased, and the amounts of both proteins
were reduced when TolC was depleted. Translational lacZ fusions showed that
TolC did not affect the synthesis of either CvaA-beta-galactosidase or
CvaB-beta-galactosidase, and CvaA or CvaB did not affect the synthesis of
CvaB-beta- galactosidase or CvaA-beta-galactosidase, respectively. However,
the stabilities of CvaA and CvaB proteins were affected by the absence of
one another and by that of TolC. The instability of CvaA was more severe in
TolC-depleted cells than in CvaB-depleted cells. On the other hand, CvaB
was less stable in the absence of CvaA than in the absence of TolC. In
addition, using a cross-linking reagent, we showed that CvaA directly
interacts with both CvaB and TolC proteins. Taken together, these data
support the hypothesized structural role of CvaA in connecting CvaB and
TolC.
Copyright © 1997, American Society for Microbiology
Interactions of dedicated export membrane proteins of the colicin V secretion system: CvaA, a member of the membrane fusion protein family, interacts with CvaB and TolC
Department of Biology, Georgia State University, Atlanta 30303, USA.
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