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 inhibit MMP. Pathogen-encoded mitochondrion-targeted proteins may or may not show amino acid sequence homology to Bcl-2-like proteins. Among the Bcl-2-unrelated, mitochondrion-targeted proteins, several interact with the voltage-dependent anion channel (VDAC) or with the adenine nucleotide translocator (ANT). While VDAC-targeted proteins show homology to VDAC/porin, ANT-targeted proteins possess relatively short cationic binding domains, which may facilitate insertion into the negatively charged inner mitochondrial membrane. It may be speculated that such proteins employ pre-existing host-intrinsic mechanisms of MMP control.