Voltage gating of Escherichia coli porin channels : role of the constriction loop

Phale, P. S. and Schirmer, T. and Prilipov, A. and Lou, K. L. and Hardmeyer, A. and Rosenbusch, J. P.. (1997) Voltage gating of Escherichia coli porin channels : role of the constriction loop. Proceedings of the National Academy of Sciences of the United States of America, Vol. 94, H. 13. pp. 6741-6745.

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Official URL: http://edoc.unibas.ch/dok/A5258275

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In the homotrimeric OmpF porin from Escherichia coli, each channel is constricted by a loop protruding into the beta-barrel of the monomer about halfway through the membrane. The water-filled channels exist in open or closed states, depending on the transmembrane potential. For the transition between these conformations, two fundamentally different mechanisms may be envisaged: a bulk movement of the constriction loop L3 or a redistribution of charges in the channel lumen. To distinguish between these hypotheses, nine mutant proteins were constructed on the basis of the high-resolution x-ray structure of the wild-type protein. Functional changes were monitored by measuring single-channel conductance and critical voltage of channel closing. Structural alterations were determined by x-ray analysis to resolutions between 3.1 and 2.1 A. Tethering the tip of L3 to the barrel wall by a disulfide bridge (E117C/A333C), mobilizing L3 by perturbing its interaction with the barrel wall (D312N, S272A, E296L), or deleting residues at the tip of the loop (Delta116-120) did not alter appreciably the sensitivity of the channels to an external potential. A physical occlusion, due to a gross movement of L3, which would cause the channels to assume a closed conformation, can therefore be excluded.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Structural Biology & Biophysics > Structural Biology (Schirmer)
UniBasel Contributors:Schirmer, Tilman
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:National Academy of Sciences
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:20
Deposited On:22 Mar 2012 13:20

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