Function of cytosolic chaperones in Tom70-mediated mitochondrial import.
The great majority of mitochondrial proteins are synthesized by cytosolic ribosomes and then imported into the organelle post-translationally. The translocase of the outer membrane (TOM) is a proteinaceous machinery that contains surface receptors for preprotein recognition and also serves as the main entry gateway into mitochondria. Mitochondrial targeting requires various cytosolic factors, in particular the molecular chaperones Hsc70/Hsp70 and Hsp90. The chaperone activity of Hsc70/Hsp70 and Hsp90 occurs in coordinated cycles of ATP hydrolysis and substrate binding, and is regulated by a number of co-chaperone proteins. The import receptor Tom70 is a member of the tetratricopeptide repeat (TPR) co-chaperone family and contains a conserved TPR clamp domain for interaction with Hsc70 and Hsp90. Such interaction is essential for the initiation of the import process. This review will discuss the roles of Hsc70 and Hsp90 in mitochondrial import and summarize recent progress in understanding these pathways.
Fan
Anna C Y
AC
Department of Biochemistry, McGill University, 3649 Promenade Sir William Osler, Montreal, Quebec H3G0B1, Canada.
Young
Jason C
JC
D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D033681:Mitochondrial Membrane Transport Proteins / Q000737:chemistry / Q000502:physiology*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D021381:Protein Transport
D050883:HSC70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; C402118:TOMM70 protein, human