Molecular chaperone Hsp70/Hsp90 prepares the mitochondrial outer membrane translocon receptor Tom71 for preprotein loading.Li, J., Qian, X., Hu, J., Sha, B.
(2009) J Biol Chem 284: 23852-23859
- PubMed: 19581297
- DOI: https://doi.org/10.1074/jbc.M109.023986
- Primary Citation of Related Structures:
3FP2, 3FP3, 3FP4
- PubMed Abstract:
The preproteins targeted to the mitochondria are transported through the translocase of the outer membrane complex. Tom70/Tom71 is a major surface receptor of the translocase of the outer membrane complex for mitochondrial preproteins. The preproteins are escorted to Tom70/Tom71 by molecular chaperones Hsp70 and Hsp90. Here we present the high resolution crystal structures of Tom71 and the protein complexes between Tom71 and the Hsp70/Hsp90 C terminus. The crystal structures indicate that Tom70/Tom71 may exhibit two distinct states. In the closed state, the N-terminal domain of Tom70/Tom71 partially blocks the preprotein-binding pocket. In the open state, the N-terminal domain moves away, and the preprotein-binding pocket is fully exposed. The complex formation between the C-terminal EEVD motif of Hsp70/Hsp90 and Tom71 could lock Tom71 in the open state where the preprotein-binding pocket of Tom71 is ready to receive preproteins. The interactions between Hsp70/Hsp90 and Tom71 N-terminal domain generate conformational changes that may increase the volume of the preprotein-binding pocket. The complex formation of Hsp70/Hsp90 and Tom71 also generates significant domain rearrangement within Tom71, which may position the preprotein-binding pocket closer to Hsp70/Hsp90 to facilitate the preprotein transfer from the molecular chaperone to Tom71. Therefore, molecular chaperone Hsp70/Hsp90 may function to prepare the mitochondrial outer membrane receptor Tom71 for preprotein loading.
Department of Cell Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294-0005, USA.