Figure 4.

Proposed model of inner-membrane mitochondrial complex biogenesis. Three types of proteins compose the inner-membrane complexes: (1) Mitochondrial-encoded proteins translated on membrane-bound mRNA, depending on specific activator proteins. (2) MLR proteins, identified in this work, are nuclear-encoded and translated in the vicinity of the outer mitochondrial membrane. (3) Nuclear-encoded proteins translated on free cytoplasmic polysomes and that are posttranslationally imported. The model assumes that pathways 1 and 2 are spatially connected, thus facilitating the formation of the core protein complex with which accessory proteins (pathway 3) will combine.