Differential requirement of membrane potential for import of the nuclear endcoded proteins into mitochondria in two developmental stages of Trypanosoma brucei

Differential Requirement of Membrane Potential for Import of the Nuclear Encoded Proteins Into Mitochondria in Two Developmental Stages of Trypanosoma brucei. Shuntae Williams and Minu Chaudhuri. Division of Microbial Pathogenesis and Immune Response, Meharry Medical College, Nashville, TN 37208 Developmental regulation of mitochondrial activities is crucial for survival of Trypanosoma brucei during their digenetic life cycle. The bloodstream form (BF) that is found in the mammalian host respires exclusively by a cytochrome‐independent, non‐proton motif terminal oxidase known as trypanosome alternative oxidase (TAO). However, upon differentiation to the procyclic form (PF) found in the insect gut, TAO is down‐regulated and the usual cytochrome dependent respiratory complexes are developed. Here, we have compared the import of TAO and cytochrome oxidase IV (Cox IV) subunit into the mitochondria of both forms under in vitro conditions. The import of these proteins into isolated PF mitochondria was dependent on the mitochondrial inner membrane potential (ψ), required proteinaceous material on the outer membrane and depended on the presence of internal and external ATP. However, the import of these proteins into the BF mitochondria was not inhibited after the mitochondrial ψ was dissipated. In contrast, import of TAO and Cox IV into mitochondria from both forms was completely abolished after the hydrolysis of ATP by apyrase or removal of the ATP and ATP‐generating system from the import buffer, suggesting that import is dependent of the presence of external ATP. Together, these data suggest that the import of proteins into mitochondria of the BF occurs by a unique mitochondrial protein import pathway.