Skip Navigation



PEDS Advance Access published online on October 6, 2004
Protein Engineering Design and Selection, doi:10.1093/protein/gzh078
This Article
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
17/9/665    most recent
gzh078v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Baslé, A.
Right arrow Articles by Delcour, A. H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Baslé, A.
Right arrow Articles by Delcour, A. H.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

Received June 11, 2004
Revised August 25, 2004
Accepted September 28, 2004

Article

Deletions of single extracellular loops affect pH-sensitivity, but not voltage-dependence, of the E. coli porin OmpF

Arnaud Baslé , Randa Qutub , Mahsa Mehrazin , Jamie Wibbenmeyer , and Anne H. Delcour *

* To whom correspondence should be addressed. E-mail: adelcour{at}uh.edu.


  Abstract

The molecular basis for the voltage- and pH dependence of the E. coli OmpF porin activity remains unknown. The L3 loop was previously shown not be involved in voltage-dependence. Here we have used seven OmpF mutants where single extracellular loops, except L3, were deleted one at the time. The proteins are expressed at levels comparable to wildtype and purified as trimers. Wildtype and mutant proteins were inserted into planar lipid bilayers for electrophysiological measurement of their activity. Current-voltage relationships show the typical porin channel closure at voltages greater than the critical voltage. Measurements of critical voltages for the seven deletion mutants showed no significant differences relative to wildtype, hence eliminating the role of single loops on voltage sensitivity. However, deletions of loops L1 or L7 or L8 affected the tendency of channels to close at acidic pH. Wildtype channels close more readily at acidic pH, and their open probability is decreased by ~ 60% at pH 4.0 relative to pH 7.0. For mutants lacking loop L1, L7 or L8, the channel open probability was found not to be significantly different at pH 4.0 than at pH 7.0. The other deletion mutants retained a pH-sensitivity similar to the wildtype channel. Possible mechanistic scenarios for the voltage- and pH-dependence of E. coli OmpF porin are discussed based on these results.

Keywords: Patch clamp; BLM; porin; mutants; modulation.
Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?


This article has been cited by other articles:


Home page
 J. Biol. Chem.Home page
J. Huff, M. Pavlenok, S. Sukumaran, and M. Niederweis
Functions of the Periplasmic Loop of the Porin MspA from Mycobacterium smegmatis
J. Biol. Chem., April 10, 2009; 284(15): 10223 - 10231.
[Abstract] [Full Text] [PDF]


Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.