title: Quaternary structure of the mitochondrial TIM23 complex reveals dynamic association between Tim23p and other subunits.
abstract: Tim23p is an essential channel-forming component of the multisubunit TIM23 complex of the mitochondrial inner membrane that mediates protein import. Radiolabeled Tim23p monocysteine mutants were imported in vitro, incorporated into functional TIM23 complexes, and subjected to chemical cross-linking. Three regions of proximity between Tim23p and other subunits of the TIM23 complex were identified: Tim17p and the first transmembrane segment of Tim23p; Tim50p and the C-terminal end of the Tim23p hydrophilic region; and the entire hydrophilic domains of Tim23p molecules. These regions of proximity reversibly change in response to changes in membrane potential across the inner membrane and also when a translocating substrate is trapped in the TIM23 complex. These structural changes reveal that the macromolecular arrangement within the TIM23 complex is dynamic and varies with the physiological state of the mitochondrion.
authors.affiliation: Department of Molecular and Cellular Medicine, Texas A&M University System Health Science Center, College Station, TX 77843-1114, USA.
authors.forename: Nathan N
authors.initials: NN
authors.lastname: Alder
authors.forename: Jennifer
authors.initials: J
authors.lastname: Sutherland
authors.forename: Ashley I
authors.initials: AI
authors.lastname: Buhring
authors.forename: Robert E
authors.initials: RE
authors.lastname: Jensen
authors.forename: Arthur E
authors.initials: AE
authors.lastname: Johnson
mesh_terms: D003432:Cross-Linking Reagents / Q000494:pharmacology; D047468:Immunoprecipitation; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008954:Models, Biological; D050505:Mutant Proteins / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism*; D013379:Substrate Specificity / Q000187:drug effects
chemical_list: D003432:Cross-Linking Reagents; D026901:Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D050505:Mutant Proteins; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; C083081:TIM23 protein, S cerevisiae