Biochemical and Biophysical Characterization of the Cell Wall Porin of Corynebacterium glutamicum: The Channel Is Formed by a Low Molecular Mass Polypeptide
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- 作者：Thomas Lichtinger ; Andreas Burkovski ; Michael Niederweis ; Reinhard Krä ; mer ; and Roland Benz
- 刊名：Biochemistry
- 出版年：1998
- 出版时间：October 27, 1998
- 年：1998
- 卷：37
- 期：43
- 页码：15024 - 15032
- 全文大小：129K
- 年卷期：v.37,no.43(October 27, 1998)
- ISSN：1520-4995
文摘
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 bilayerexperiments, in the cell envelope fractions isolated by sucrose-density centrifugations and in organic solventof whole cells. It was purified to homogeneity by fast-protein liquid chromatography across a Mono-Qcolumn. 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 accordingto partial sequencing no significant homology to known protein sequences. The purified protein formedlarge ion-permeable channels in lipid bilayer membranes from phosphatidylcholine/phosphatidylserinemixtures with a single-channel conductance of 5.5 nS in 1 M KCl. Experiments with different saltssuggested that the cell wall channel of C. glutamicum was highly cation-selective caused by negativecharges localized at the channel mouth. The analysis of the single-channel conductance data using theRenkin 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 containpoint net charges.