An interplay between the TOM complex and porin isoforms in the yeast Saccharomyces cerevisiae mitochondria

The outer mitochondrial membrane of Saccharomyces cerevisiae contains two isoforms of mitochondrial porin, known also as the voltage-dependent anion channel. The isoform termed here porinl displays channel-forming activity enabling metabolite transport whereas the second one, termed here porin2, does not form a channel and its function is still not clear, We have shown recently that in the absence of porinl, the channel within the protein import machinery (the TOM complex) is essential for metabolite transport across the outer membrane [Kmita and Budzinska, Biochim, Biophys. Acta 1509 (2000) 6044-6050]. Here, we report that the TOM complex channel may also serve as a supplementary pathway for metabolites in the presence of porinl when the permeability of the latter is limited and the role of the TOM complex seems to increase when porin2 is depleted, (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. AU rights reserved.