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First published online November 21, 2007
doi: 10.1242/10.1242/jcs.018929

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Biogenesis of yeast dicarboxylate carrier: the carrier signature facilitates translocation across the mitochondrial outer membrane

Vincenzo Zara^1,*, Alessandra Ferramosca¹, Loredana Capobianco^1,2, Katrin M. Baltz^3,, Olga Randel³, Joachim Rassow³, Ferdinando Palmieri² and Panagiotis Papatheodorou³

¹ Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, Via Provinciale Lecce-Monteroni, I-73100 Lecce, Italy
² Dipartimento Farmaco-Biologico, Università di Bari, I-70125 Bari, Italy
³ Institut für Physiologische Chemie, Medizinische Fakultät der Ruhr-Universität Bochum, D-44780 Bochum, Germany

^* Author for correspondence (e-mail: vincenzo.zara{at}unile.it)

Accepted 17 September 2007

A family of related carrier proteins mediates the exchange of metabolites across the mitochondrial inner membrane. The carrier signature Px[D/E]xx[K/R] is a highly conserved sequence motif in all members of this family. To determine its function in the biogenesis of carrier proteins, we used the dicarboxylate carrier (DIC) of yeast as a model protein. We found that the carrier signature was dispensable in binding of the newly synthesized protein to the import receptor Tom70, but that it was specifically required for efficient translocation across the mitochondrial outer membrane. To determine the relevance of individual amino acid residues of the carrier signature in the transport activity of the protein, we exchanged defined residues with alanine and reconstituted the mutant proteins in vitro. Substitution of the carrier signature in helix H1 reduced the transport activity for [³³P]-phosphate by approximately 90% and an additional substitution of the carrier signature in helix H5 blocked the transport activity completely. We conclude that the carrier signature of the dicarboxylate carrier is involved both in the biogenesis and in the transport activity of the functional protein.

Key words: Mitochondria, Metabolite carrier proteins, Carrier signature

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