PorH, a new channel-forming protein present in the cell wall of Corynebacterium efficiens and Corynebacterium callunae

1 Lehrstuhl für Biotechnologie, Biozentrum der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany 2 Max-Planck-Institute for Biochemistry, Department for Protein Analytics, Am Klopferspitz 18A, D-82152 Martinsried, Germany Correspondence Roland Benz roland.benz{at}mail.uni-wuerzburg.de Corynebacterium callunae and Corynebacterium efficiens are close relatives of the glutamate-producing mycolata species Corynebacterium glutamicum . The properties of the pore-forming proteins, extracted by organic solvents, were studied. The cell extracts contained channel-forming proteins that formed ion-permeable channels with a single-channel conductance of about 2 to 3 nS in 1 M KCl in a lipid bilayer assay. The corresponding proteins from both corynebacteria were purified to homogeneity and were named PorH C.call and PorH C.eff . Electrophysiological studies of the channels suggested that they are wide and water-filled. Channels formed by PorH C.call are cation-selective, whereas PorH C.eff forms slightly anion-selective channels. Both proteins were partially sequenced. A multiple sequence alignment search within the known chromosome of C. efficiens demonstrated that it contains a gene that fits the partial amino acid sequence of PorH C.eff . PorH C.call shows high homology to PorH C.eff . PorH C.eff is encoded in the bacterial chromosome by a gene that is localized within the vicinity of the porA gene of C. efficiens . PorH C.eff has no signal sequence at the N terminus, which means that it is not exported by the Sec-secretion pathway. The structure of PorH in the cell wall of the corynebacteria is discussed. Abbreviations: LDAO, N , N -dimethyldodecylamine- N -oxide; PC, diphytanoyl phosphatidylcholine The GenBank/EMBL/DDBJ accession numbers for the sequences reported in this paper are AJ871585 and AJ871586 .