This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.104.041384v1 87/5/3137    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Miedema, H. Articles by Meijberg, W. Search for Related Content PubMed PubMed Citation Articles by Miedema, H. Articles by Meijberg, W.

Permeation Properties of an Engineered Bacterial OmpF Porin Containing the EEEE-Locus of Ca²⁺ Channels

Henk Miedema ^*, Anita Meter-Arkema ^*, Jenny Wierenga ^*, John Tang , Bob Eisenberg , Wolfgang Nonner , Hans Hektor ^*, Dirk Gillespie   and Wim Meijberg ^*

^* Biomade Technology Foundation, Groningen, The Netherlands; Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois; and Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida

Correspondence: Address reprint requests to Henk Miedema, Nijenborgh 4, 9747 AG, Groningen, The Netherlands. E-mail: miedema{at}biomade.nl.

The selectivity filter of the bacterial porin OmpF carries a small net charge close to –1 e and is therefore only slightly cation-selective. Calcium channels, on the other hand, contain four negatively charged glutamates, the EEEE-locus, and are among the most selective cation channels known. We aimed to turn the essentially nonselective OmpF into a Ca²⁺-selective channel. To that end, two additional glutamates (R42E and R132E) were introduced in the OmpF constriction zone that already contains D113 and E117. Mutant OmpF containing this DEEE-locus has a high Ca²⁺ over Cl^– selectivity and a Na⁺ current with a strongly increased sensitivity to 1 mM Ca²⁺. The charge/space competition model, initially applied to the L-type Ca²⁺ channel, identifies the fixed charge and filter volume as key determinants of ion selectivity, with the precise atomic arrangement having only second-order effects. By implication, the reproduction of fixed charge and filter volume should transform two channels into channels of similar selectivity, even if the two belong to entirely different ion channel families, as is the case for OmpF and the L-type Ca²⁺ channel. The results presented here fit quite well in the framework of charge/space competition theory.

This article has been cited by other articles:

				B. Eisenberg Engineering channels: Atomic biology PNAS, April 29, 2008; 105(17): 6211 - 6212. [Full Text] [PDF]

				D. Gillespie Energetics of Divalent Selectivity in a Calcium Channel: The Ryanodine Receptor Case Study Biophys. J., February 15, 2008; 94(4): 1169 - 1184. [Abstract] [Full Text] [PDF]

				D. Boda, W. Nonner, M. Valisko, D. Henderson, B. Eisenberg, and D. Gillespie Steric Selectivity in Na Channels Arising from Protein Polarization and Mobile Side Chains Biophys. J., September 15, 2007; 93(6): 1960 - 1980. [Abstract] [Full Text] [PDF]

				H. Miedema, M. Vrouenraets, J. Wierenga, D. Gillespie, B. Eisenberg, W. Meijberg, and W. Nonner Ca2+ Selectivity of a Chemically Modified OmpF with Reduced Pore Volume Biophys. J., December 15, 2006; 91(12): 4392 - 4400. [Abstract] [Full Text] [PDF]

				E. K. Schmitt, M. Vrouenraets, and C. Steinem Channel Activity of OmpF Monitored in Nano-BLMs Biophys. J., September 15, 2006; 91(6): 2163 - 2171. [Abstract] [Full Text] [PDF]

				M. Vrouenraets, J. Wierenga, W. Meijberg, and H. Miedema Chemical Modification of the Bacterial Porin OmpF: Gain of Selectivity by Volume Reduction Biophys. J., February 15, 2006; 90(4): 1202 - 1211. [Abstract] [Full Text] [PDF]