Viral and bacterial proteins regulating apoptosis at the mitochondrial level

Mitochondrial membrane permeabilization (MMP) is a critical step of several apoptotic pathways. Some infectious intracellular pathogens can regulate ( induce or inhibit) apoptosis of their host cells at the mitochondrial level , by targeting proteins to mitochondrial membranes that either induce or in hibit MMP. Pathogen-encoded mitochondrion-targeted proteins may or may not show amino acid sequence homology to Bcl-2-like proteins. Among the Bcl-2-u nrelated, mitochondrion-targeted proteins, several interact with the voltag e-dependent anion channel (VDAC) or with the adenine nucleotide translocato r (ANT). While VDAC-targeted proteins show homology to VDAC/porin, ANT-targ eted proteins possess relatively short cationic binding domains, which may facilitate insertion into the negatively charged inner mitochondrial membra ne. It may be speculated that such proteins employ pre-existing host-intrin sic mechanisms of MMP control.