Nature Structural & Molecular Biology11, 226 - 233 (2004)
Published online: 15 February 2004; | doi:10.1038/nsmb735
Pam16 has an essential role in the mitochondrial protein import motor
Ann E Frazier1, 2, 8, Jan Dudek1, 2, 8, Bernard Guiard3, Wolfgang Voos1, Yanfeng Li1, 2, Maria Lind1, 7, Chris Meisinger1, Andreas Geissler1, 7, Albert Sickmann4, 5, Helmut E Meyer4, Virginia Bilanchone6, Michael G Cumsky6, Kaye N Truscott1, Nikolaus Pfanner1
& Peter Rehling1
1
Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany.
2
Fakultät für Biologie, Universität Freiburg, D-79104 Freiburg, Germany.
3
Laboratoire propre du CNRS Université Pierre et Marie Curie, F-91190 Gif-sur-Yvette, France.
5
Rudolf-Virchow-Center for Experimental Biomedicine, Universität Würzburg, D-97078 Würzburg, Germany.
6
Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California 92697-3900, USA.
7
Present addresses: Department of Comparative Physiology, Evolutionary Biology Centre, Uppsala University, SE-75236 Uppsala, Sweden (M.L.) and Curacyte AG, D-80339 München, Germany (A.G.).
Mitochondrial preproteins destined for the matrix are translocated by two channel-forming transport machineries, the translocase of the outer membrane and the presequence translocase of the inner membrane. The presequence translocase-associated protein import motor (PAM) contains four essential subunits: the matrix heat shock protein 70 (mtHsp70) and its three cochaperones Mge1, Tim44 and Pam18. Here we report that the PAM contains a fifth essential subunit, Pam16 (encoded by Saccharomyces cerevisiae YJL104W), which is selectively required for preprotein translocation into the matrix, but not for protein insertion into the inner membrane. Pam16 interacts with Pam18 and is needed for the association of Pam18 with the presequence translocase and for formation of a mtHsp70−Tim44 complex. Thus, Pam16 is a newly identified type of motor subunit and is required to promote a functional PAM reaction cycle, thereby driving preprotein import into the matrix.
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