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Structure–function of cyanobacterial outer‐membrane protein, Slr1270: Homolog of Escherichia coli drug export/colicin import protein, TolC
Author(s) -
Agarwal Rachna,
Zakharov Stanislav,
Hasan S. Saif,
Ryan Christopher M.,
Whitelegge Julian P.,
Cramer William A.
Publication year - 2014
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2014.08.028
Subject(s) - colicin , escherichia coli , bacterial outer membrane , biophysics , chemistry , porin , ion channel , biochemistry , membrane protein , inner membrane , conductance , protein secondary structure , transport protein , thylakoid , biology , membrane , chloroplast , gene , receptor , mathematics , combinatorics
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.