Conductance and selectivity fluctuations in D127 mutants of the bacterial porin OmpF

Miedema, Henk and Vrouenraets, Maarten and Wierenga, Jenny and Eisenberg, Bob and Schirmer, Tilman and Baslé, Arnaud and Meijberg, Wim. (2006) Conductance and selectivity fluctuations in D127 mutants of the bacterial porin OmpF. European biophysics journal, Vol. 36, H. 1. pp. 13-22.

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Official URL: http://edoc.unibas.ch/dok/A5258238

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A recent molecular dynamics study questioned the protonation state and physiological role of aspartate 127 (D127) of E. coli porin OmpF. To address that question we isolated two OmpF mutants with D127 either neutralized (D127N) or replaced by a positively charged lysine (D127K). The charge state of the residue at position 127 has clear effects on both conductance and selectivity. The D127K but not the D127N mutant expresses resilient conductance and selectivity fluctuations. These fluctuations reflect, we think, either changes in the ionization state of K127 and/or transitions between unstable subconformations as induced by the electrostatic repulsion between two positively charged residues, K127 and the nearby R167. Our results slightly favor the view that in WT OmpF residue D127 is deprotonated. As for the role of D127 in OmpF functionality, the gating of both mutants shows very similar sensitivity toward voltage as WT OmpF. Moreover, the current fluctuations of the D127K mutant were observed also in the absence of an applied electric field. We therefore dismiss D127 as a key residue in the control mechanism of the voltage-dependent gating of OmpF.
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
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:07 Aug 2015 12:05
Deposited On:22 Mar 2012 13:30

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