Mitochondrial Import Driving Forces: Enhanced Trapping by Matrix Hsp70 Stimulates Translocation and Reduces the Membrane Potential Dependence of Loosely Folded Preproteins
AUTOR(ES)
Geissler, Andreas
FONTE
American Society for Microbiology
RESUMO
The mitochondrial heat shock protein Hsp70 (mtHsp70) is essential for driving translocation of preproteins into the matrix. Two models, trapping and pulling by mtHsp70, are discussed, but positive evidence for either model has not been found so far. We have analyzed a mutant mtHsp70, Ssc1-2, that shows a reduced interaction with the membrane anchor Tim44, but an enhanced trapping of preproteins. Unexpectedly, at a low inner membrane potential, ssc1-2 mitochondria imported loosely folded preproteins more efficiently than wild-type mitochondria. The import of a tightly folded preprotein, however, was not increased in ssc1-2 mitochondria. Thus, enhanced trapping by mtHsp70 stimulates the import of loosely folded preproteins and reduces the dependence on the import-driving activity of the membrane potential, directly demonstrating that trapping is one of the molecular mechanisms of mtHsp70 action.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=99885Documentos Relacionados
- Mitochondrial GrpE modulates the function of matrix Hsp70 in translocation and maturation of preproteins.
- The mitochondrial Hsp70-dependent import system actively unfolds preproteins and shortens the lag phase of translocation
- Dynamic interaction between Isp45 and mitochondrial hsp70 in the protein import system of the yeast mitochondrial inner membrane.
- Protein unfolding by mitochondria: The Hsp70 import motor
- Differential requirement for the mitochondrial Hsp70-Tim44 complex in unfolding and translocation of preproteins.