The TIM17.23 preprotein translocase of mitochondria: composition and function in protein transport into the matrix.
We have analysed the structural organization of the TIM17.23 complex, the preprotein translocase of the mitochondrial inner membrane specific for protein targeting to the matrix. The components Tim17, Tim23 and Tim44 are present in this complex in equimolar amounts. A sub-complex containing Tim23 and Tim44 but no Tim17, or a sub-complex containing Tim23 and Tim17 but no Tim44 was not detected. Tim44 is peripherally associated at the matrix side. Tim44 forms dimers which recruit two molecules of mt-Hsp70 to the sites of protein import. A sequential, hand-over-hand mode of interaction of these two mt-Hsp70.Tim44 complexes with a translocating polypeptide chain is proposed.
Moro
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F
Institut für Physiologische Chemie der Universität München, Goethestrasse 33, 80336 München, Germany.
Sirrenberg
C
C
Schneider
H C
HC
Neupert
W
W
Brunner
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M
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D019281:Dimerization; D010450:Endopeptidases / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D007425:Intracellular Membranes / Q000201:enzymology; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008954:Models, Biological; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009994:Osmolar Concentration; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism*; D012097:Repressor Proteins; D012441:Saccharomyces cerevisiae / Q000166:cytology; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D012995:Solubility
D002352:Carrier Proteins; D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D011498:Protein Precursors; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; C091191:TIM17 protein, S cerevisiae; C083081:TIM23 protein, S cerevisiae; C077016:TIM44 protein, S cerevisiae; D010450:Endopeptidases