Structure-function of cyanobacterial outer-membrane protein, Slr1270: homolog of Escherichia coli drug export/colicin import protein, TolC

FEBS Lett. 2014 Nov 3;588(21):3793-801. doi: 10.1016/j.febslet.2014.08.028. Epub 2014 Sep 13.

Abstract

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 80-200pS, 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.

Keywords: Cyanobacteria; Ion channel; Outer-membrane proteins; Secondary-structure; Slr1270; TolC.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Outer Membrane Proteins / chemistry*
  • Bacterial Outer Membrane Proteins / metabolism*
  • Escherichia coli Proteins / chemistry*
  • Lipid Bilayers / metabolism
  • Membrane Transport Proteins / chemistry*
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Multimerization
  • Protein Refolding
  • Protein Structure, Quaternary
  • Protein Structure, Secondary
  • Sequence Alignment
  • Sequence Homology, Amino Acid*
  • Synechocystis / chemistry*

Substances

  • Bacterial Outer Membrane Proteins
  • Escherichia coli Proteins
  • Lipid Bilayers
  • Membrane Transport Proteins
  • tolC protein, E coli