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

<jats:p><jats:italic>Corynebacterium callunae</jats:italic>and<jats:italic>Corynebacterium efficiens</jats:italic>are close relatives of the glutamate-producing mycolata species<jats:italic>Corynebacterium glutamicum</jats:italic>. 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<jats:sub>C.call</jats:sub>and PorH<jats:sub>C.eff</jats:sub>. Electrophysiological studies of the channels suggested that they are wide and water-filled. Channels formed by PorH<jats:sub>C.call</jats:sub>are cation-selective, whereas PorH<jats:sub>C.eff</jats:sub>forms slightly anion-selective channels. Both proteins were partially sequenced. A multiple sequence alignment search within the known chromosome of<jats:italic>C. efficiens</jats:italic>demonstrated that it contains a gene that fits the partial amino acid sequence of PorH<jats:sub>C.eff</jats:sub>. PorH<jats:sub>C.call</jats:sub>shows high homology to PorH<jats:sub>C.eff</jats:sub>. PorH<jats:sub>C.eff</jats:sub>is encoded in the bacterial chromosome by a gene that is localized within the vicinity of the<jats:italic>porA</jats:italic>gene of<jats:italic>C. efficiens</jats:italic>. PorH<jats:sub>C.eff</jats:sub>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.</jats:p>