Compared to thylakoid and inner membrane proteins in cyanobacteria, no structure-function information is available presently for integral outer-membrane proteins (OMPs). The Slr1270 protein from the cyanobacterium Synechocystis 6803, over-expressed in Escherichia coli, was refolded, and characterized for molecular size, secondary structure, and ion-channel function. Refolded Slr1270 displays a single band in native-electrophoresis, has an α-helical content of 50-60%, as in E. coli TolC with which it has significant secondary-structure similarity, and an ion-channel function with a single-channel conductance of 80-200 pS, and a monovalent ion (K+:Cl-) selectivity of 4.7:1. The pH-dependence of channel conductance implies a role for carboxylate residues in channel gating, analogous to that in TolC. 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
Agarwal, R., Zakharov, S., Hasan, S. S., Ryan, C. M., Whitelegge, J. P., & Cramer, W. A. (2014). Structure-function of cyanobacterial outer-membrane protein, Slr1270: Homolog of Escherichia coli drug export/colicin import protein, TolC. FEBS Letters, 588(21), 3793–3801. https://doi.org/10.1016/j.febslet.2014.08.028