INACTIVATION OF THE PEPTIDE-SENSITIVE CHANNEL FROM THE YEAST MITOCHONDRIAL OUTER-MEMBRANE - PROPERTIES, SENSITIVITY TO TRYPSIN AND MODULATION BY A BASIC PEPTIDE

The yeast Peptide Sensitive Channel (PSC), a cationic channel of the m itochondrial outer membrane closes with slow kinetics at potentials of either polarity. The properties of this inactivation closely resemble those of the Voltage-Dependent Anion Channel (VDAC) slow kinetics clo sures. Addition of trypsin to one compartment suppresses the inactivat ion observed when this compartment is made positive, but does not affe ct the inactivation observed at potentials of reverse polarity. Both s ides of the channel are sensitive. The reduced form of the Mast Cell D egranulating peptide (rMCD) increases the rate of inactivation, but on ly when the polarity of the compartment to which it is added is positi ve. The effect is not reversed by washing the peptide out, but is supp ressed by trypsin. The peptide can bind to both sides of the membrane. The effect of rMCD on PSC closely resembles that of the ''modulator'' on VDAC. The similarities between PSC and VDAC suggest that the forme r might be a cationic porin of the mitochondrial outer membrane posses sing a structure closely related to that of VDAC.