HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 278, Issue 19, 17539-17545, May 9, 2003

This Article Full Text Full Text (PDF) All Versions of this Article: 278/19/17539    most recent M301202200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Simonet, V. C. Articles by Delcour, A. H. Search for Related Content PubMed PubMed Citation Articles by Simonet, V. C. Articles by Delcour, A. H. Social Bookmarking                      What's this?

The Vibrio cholerae Porins OmpU and OmpT Have Distinct Channel Properties^*

Valérie C. Simonet, Arnaud Baslé, Karl E. Klose^§, and Anne H. Delcour^¶

From the  Department of Biology and of Biochemistry, University of Houston, Houston, Texas 77204-5001 and the ^§ Department of Microbiology and Immunology, University of Texas Health Science Center, San Antonio, Texas 78229-3900

Numerous environmental signals regulate the production of virulence factors and the composition of the outer membrane of Vibrio cholerae. In particular, bile promotes the ToxR-dependent expression of the porin OmpU. Strains expressing solely OmpU are more resistant to bile, are better able to colonize the intestine, and produce more cholera toxin than strains expressing solely the OmpT porin. To gain some understanding in the physiological relevance and the molecular mechanism underlying these porin-dependent phenotypes, we have undertaken a thorough electrophysiological characterization of the channel properties of the two porins. Purified OmpU or OmpT was reconstituted in liposomes suitable for patch clamp and in planar lipid bilayers. The high resolution of the patch clamp technique allowed us to analyze in detail the behavior of single OmpU and OmpT channels. Both channels exhibit closing transitions to various conductance states. OmpT is a much more dynamic channel than OmpU, displaying frequent and prolonged closures, even at low transmembrane potentials. With a critical voltage for closure V_c of approximately ±90 mV, OmpT is much more voltage-sensitive than OmpU (with a V_c of approximately ±160 mV), a feature that is also readily apparent in the voltage dependence of closing probability observed in patch clamp in the ±100 mV range. OmpT has low ionic selectivity (P_K/P_Cl = ~4), whereas OmpU is more cation-selective (P_K/P_Cl = ~14). The distinct functional properties of the two porins are likely to play an integrated role with environmental regulation of their expression. For example, the higher selectivity of OmpU for cations provides a possible explanation for the protective role played by this porin in a bile-containing environment, because this type of selectivity would restrict the flux of anionic bile salts through the outer membrane and thus would reduce the exposure of the cytoplasmic membrane to this natural detergent.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				G. Duret, M. Szymanski, K.-J. Choi, H.-J. Yeo, and A. H. Delcour The TpsB Translocator HMW1B of Haemophilus influenzae Forms a Large Conductance Channel J. Biol. Chem., June 6, 2008; 283(23): 15771 - 15778. [Abstract] [Full Text] [PDF]

				M. Pagel, V. Simonet, J. Li, M. Lallemand, B. Lauman, and A. H. Delcour Phenotypic Characterization of Pore Mutants of the Vibrio cholerae Porin OmpU J. Bacteriol., December 1, 2007; 189(23): 8593 - 8600. [Abstract] [Full Text] [PDF]

				G. Duret and A. H. Delcour Deoxycholic Acid Blocks Vibrio cholerae OmpT but Not OmpU Porin J. Biol. Chem., July 21, 2006; 281(29): 19899 - 19905. [Abstract] [Full Text] [PDF]

				B. Nandi, R. K. Nandy, A. Sarkar, and A. C. Ghose Structural features, properties and regulation of the outer-membrane protein W (OmpW) of Vibrio cholerae Microbiology, September 1, 2005; 151(9): 2975 - 2986. [Abstract] [Full Text] [PDF]

				A. Basle, R. Qutub, M. Mehrazin, J. Wibbenmeyer, and A. H. Delcour Deletions of single extracellular loops affect pH sensitivity, but not voltage dependence, of the Escherichia coli porin OmpF Protein Eng. Des. Sel., September 1, 2004; 17(9): 665 - 672. [Abstract] [Full Text] [PDF]

				J. Mathur and M. K. Waldor The Vibrio cholerae ToxR-Regulated Porin OmpU Confers Resistance to Antimicrobial Peptides Infect. Immun., June 1, 2004; 72(6): 3577 - 3583. [Abstract] [Full Text] [PDF]

				H. Nikaido Molecular Basis of Bacterial Outer Membrane Permeability Revisited Microbiol. Mol. Biol. Rev., December 1, 2003; 67(4): 593 - 656. [Abstract] [Full Text] [PDF]