View the Current Issue

Article

  • The EMBO Journal (2003) 22, 816 - 825
  • doi:10.1093/emboj/cdg090

Tim50, a novel component of the TIM23 preprotein translocase of mitochondria

Dejana Mokranjac1, Stefan A. Paschen1, Christian Kozany1, Holger Prokisch1, Suzanne C. Hoppins2, Frank E. Nargang2, Walter Neupert1 and Kai Hell1

  1. Adolf-Butenandt-Institut, Lehrstuhl für Physiologische Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5, D-81377 München, Germany
  2. Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada

Correspondence to:

Walter Neupert, E-mail: Neupert@bio.med.uni-muenchen.de

Received 11 November 2002; Accepted 20 December 2002; Revised 19 December 2002

The preprotein translocase of the inner membrane of mitochondria (TIM23 complex) is the main entry gate for proteins of the matrix and the inner membrane. We isolated the TIM23 complex of Neurospora crassa. Besides Tim23 and Tim17, it contained a novel component, referred to as Tim50. Tim50 spans the inner membrane with a single transmembrane segment and exposes a large hydrophilic domain in the intermembrane space. Tim50 is essential for viability of yeast. Mitochondria from cells depleted of Tim50 displayed strongly reduced import kinetics of preproteins using the TIM23 complex. Tim50 could be cross-linked to preproteins that were halted at the level of the translocase of the outer membrane (TOM complex) or spanning both TOM and TIM23 complexes. We suggest that Tim50 plays a crucial role in the transfer of preproteins from the TOM complex to the TIM23 complex through the intermembrane space.

  • Keywords:

    • import,
    • mitochondria,
    • TIM23 complex,
    • Tim50,
    • translocation