The three domains of the mitochondrial outer membrane protein Mim1 have discrete functions in assembly of the TOM complex

Lueder, Franziska; Lithgow, Trevor

doi:10.1016/j.febslet.2009.03.064

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Volume 583, Issue 9 , Pages 1475-1480, 6 May 2009

The three domains of the mitochondrial outer membrane protein Mim1 have discrete functions in assembly of the TOM complex

Edited by Ulrike Kutay

Department of Biochemistry and Molecular Biology, Monash University, Clayton 3800, Australia

Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville 3010, Australia

Received 25 January 2009; received in revised form 18 March 2009; accepted 27 March 2009. published online 02 April 2009.

Abstract

The assembly of mitochondrial outer membrane proteins is an essential process, mediated by the SAM complex and a set of additional protein modules. We show that one of these, Mim1, is anchored in the outer membrane with its N-terminus exposed to the cytosol and its C-terminus in the mitochondrial intermembrane space. Using an in vitro assay to measure the multi-step pathway for assembly of Tom40 into the TOM complex, we find that an “early reaction” mediated by the SAM complex is regulated by the N-terminal domain of Mim1. In addition, a “late reaction” catalysed by the Sam37 subunit of the SAM complex is also influenced by Mim1. Thus, Mim1 participates at multiple stages in the assembly of the TOM complex.

Keywords: Protein import, β-Barrel protein, Mitochondria, SAM complex, Outer membrane, Membrane protein assembly