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Activity modulation of certain ion-pore forming proteins by electric properties of artificial lipid membranes

L. MEREUTA1, R. CHIRIAC1, T. LUCHIAN1,*

Affiliation

  1. 'Al. I. Cuza' University, Faculty of Physics, Laboratory of Biophysics & Medical Physics, Blvd. King Carol I, No. 11, Iasi, R-700506, Romania

Abstract

Lipid-based artificial systems built to resemble closely biological membranes represent a hot-spot of today’s biophysics research on lipid membranes-proteins interactions. Due to the interfacial chemical heterogeneity of the interface separating lipid membranes from aqueous media, membrane-penetrating peptides will sense a steep change in environmental polarity manifested via electrical interactions with the surface and dipole potential of membranes. We demonstrate that such interactions visibly modulate the membrane insertion of certain antimicrobial peptides. The effect of pH on artificial lipid membrane electrical properties was examined by studying the electrical conductance of alamethicin nanopores embedded in artificial lipid membranes. Our data strongly support the paradigm of a pH-dependent variation of the membrane dipole potential which, in conjunction with possible lateral pressure effects within the lipid membrane, lead to a non-monotonic modulation of ion transport mediated by alamethicin. By quantifying time-resolved discrete conductance fluctuations of the OmpF porin, our data point to a dipole potential-induced change of the protonation probability of acidic residues which define the constriction zone of the porin. Our interpretation points to a shift in the pKa values of such acidic residues caused most likely by alterations of the electric field profile through the OmpF pore, which in turn will lead to a change in the local concentration of hydrogen ions..

Keywords

Protein pores, Lipid membranes, Alamethicin, Electrophysiology.

Submitted at: April 1, 2008
Accepted at: July 1, 2008

Citation

L. MEREUTA, R. CHIRIAC, T. LUCHIAN, Activity modulation of certain ion-pore forming proteins by electric properties of artificial lipid membranes, Journal of Optoelectronics and Advanced Materials Vol. 10, Iss. 7, pp. 1837-1842 (2008)