Biochemical and biophysical characterization of the cell wall porin of Corynebacterium glutamicum: The channel is formed by a low molecular mass polypeptide

Academic Article

Abstract

  • The cell wall of the Gram-positive bacterium Corynebacterium glutamicum contains a channel (porin) for the passage of hydrophilic solutes. The channel-forming protein was identified, by lipid bilayer experiments, in the cell envelope fractions isolated by sucrose-density centrifugations and in organic solvent of whole cells. It was purified to homogeneity by fast- protein liquid chromatography across a Mono-Q column. The pure protein had a rather low molecular mass of about 5 kDa as judged by SDS-PAGE, which suggested that the cell wall channel is formed by a protein oligomer. The monomer has according to partial sequencing no significant homology to known protein sequences. The purified protein formed large ion-permeable channels in lipid bilayer membranes from phosphatidylcholine/phosphatidylserine mixtures with a single-channel conductance of 5.5 nS in 1 M KCl. Experiments with different salts suggested that the cell wall channel of C. glutamicum was highly cation-selective caused by negative charges localized at the channel mouth. The analysis of the single-channel conductance data using the Renkin correction factor suggested that the diameter of the cell wall channel is about 2.2 nm. Channel-forming properties of the cell wall channel of C. glutamicum were compared with those of mycobacteria. These channels share common features because they form large and water-filled channels that contain point net charges.
  • Published In

  • Biochemistry  Journal
  • Digital Object Identifier (doi)

    Author List

  • Lichtinger T; Burkovski A; Niederweis M; Kr├ímer R; Benz R
  • Start Page

  • 15024
  • End Page

  • 15032
  • Volume

  • 37
  • Issue

  • 43