title: Comparison of the protein-unfolding pathways between mitochondrial protein import and atomic-force microscopy measurements.
abstract: Many newly synthesized proteins have to become unfolded during translocation across biological membranes. We have analyzed the effects of various stabilization/destabilization mutations in the Ig-like module of the muscle protein titin upon its import from the N terminus or C terminus into mitochondria. The effects of mutations on the import of the titin module from the C terminus correlate well with those on forced mechanical unfolding in atomic-force microscopy (AFM) measurements. On the other hand, as long as turnover of the mitochondrial Hsp70 system is not rate-limiting for the import, import of the titin module from the N terminus is sensitive to mutations in the N-terminal region but not the ones in the C-terminal region that affect resistance to global unfolding in AFM experiments. We propose that the mitochondrial-import system can catalyze precursor-unfolding by reducing the stability of unfolding intermediates.
authors.affiliation: Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Sato
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Esaki
authors.forename: Julio M
authors.initials: JM
authors.lastname: Fernandez
authors.forename: Toshiya
authors.initials: T
authors.lastname: Endo
mesh_terms: D064211:Connectin; D018625:Microscopy, Atomic Force; D008928:Mitochondria / Q000378:metabolism*; D008958:Models, Molecular; D009124:Muscle Proteins / Q000737:chemistry / Q000378:metabolism*; D016296:Mutagenesis; D017510:Protein Folding; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D021381:Protein Transport; D012441:Saccharomyces cerevisiae
chemical_list: D064211:Connectin; D009124:Muscle Proteins; D011494:Protein Kinases