Pam16 has an essential role in the mitochondrial protein import motor

Nat Struct Mol Biol. 2004 Mar;11(3):226-33. doi: 10.1038/nsmb735. Epub 2004 Feb 15.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Carrier Proteins / metabolism
  • HSP70 Heat-Shock Proteins / metabolism
  • Intracellular Membranes / metabolism
  • Membrane Proteins / metabolism
  • Membrane Transport Proteins / metabolism
  • Membrane Transport Proteins / physiology*
  • Mitochondria / metabolism
  • Mitochondria / ultrastructure
  • Mitochondrial Membrane Transport Proteins
  • Mitochondrial Proteins / metabolism
  • Mitochondrial Proteins / physiology*
  • Molecular Motor Proteins / metabolism
  • Protein Binding
  • Protein Precursors / metabolism
  • Protein Transport
  • Saccharomyces cerevisiae Proteins / metabolism
  • Saccharomyces cerevisiae Proteins / physiology
  • Yeasts / chemistry
  • Yeasts / metabolism
  • Yeasts / ultrastructure


  • Carrier Proteins
  • HSP70 Heat-Shock Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • Mitochondrial Membrane Transport Proteins
  • Mitochondrial Proteins
  • Molecular Motor Proteins
  • PAM18 J protein, S cerevisiae
  • Pam16 protein, S cerevisiae
  • Protein Precursors
  • Saccharomyces cerevisiae Proteins