Sorting switch of mitochondrial presequence translocase involves coupling of motor module to respiratory chain.
The mitochondrial presequence translocase transports preproteins to either matrix or inner membrane. Two different translocase forms have been identified: the matrix transport form, which binds the heat-shock protein 70 (Hsp70) motor, and the inner membrane-sorting form, which lacks the motor but contains translocase of inner mitochondrial membrane 21 (Tim21). The sorting form interacts with the respiratory chain in a Tim21-dependent manner. It is unknown whether the respiratory chain-bound translocase transports preproteins and how the switch between sorting form and motor form occurs. We report that the respiratory chain-bound translocase contains preproteins in transit and, surprisingly, not only sorted but also matrix-targeted preproteins. Presequence translocase-associated motor (Pam) 16 and 18, two regulatory components of the six-subunit motor, interact with the respiratory chain independently of Tim21. Thus, the respiratory chain-bound presequence translocase is not only active in preprotein sorting to the inner membrane but also in an early stage of matrix translocation. The motor does not assemble en bloc with the translocase but apparently in a step-wise manner with the Pam16/18 module before the Hsp70 core.
Wiedemann
Nils
N
Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Freiburg, Germany.
van der Laan
Martin
M
Hutu
Dana P
DP
Rehling
Peter
P
Pfanner
Nikolaus
N
D004579:Electron Transport / Q000502:physiology; D014450:Electron Transport Complex III / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism* / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism* / Q000502:physiology; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D021381:Protein Transport; D012097:Repressor Proteins / Q000378:metabolism* / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000502:physiology
D018840:HSP70 Heat-Shock Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; C480348:PAM18 J protein, S cerevisiae; C484526:Pam16 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; C083081:TIM23 protein, S cerevisiae; C500397:Tim21 protein, S cerevisiae; D014450:Electron Transport Complex III