AtCCMA Interacts with AtCcmB to Form a Novel Mitochondrial ABC Transporter Involved in Cytochrome c Maturation in Arabidopsis

Naganand Rayapuram,,Jérémie Hagenmuller,,Jean-Michel Grienenberger,Philippe Giegé,Géraldine Bonnard

doi:10.1074/jbc.m704091200

Abstract

ABC transporters make a large and diverse family of proteins found in all phylae. AtCCMA is the nucleotide binding domain of a novel Arabidopsis mitochondrial ABC transporter. It is encoded in the nucleus and imported into mitochondria. Sub-organellar and topology studies find AtCCMA bound to the mitochondrial inner membrane, facing the matrix. AtCCMA exhibits an ATPase activity, and ATP/Mg(2+) can facilitate its dissociation from membranes. Blue Native PAGE shows that it is part of a 480-kDa complex. Yeast two-hybrid assays reveal interactions between AtCCMA and domains of CcmB, the mitochondria-encoded transmembrane protein of a conserved ABC transporter. All these properties designate the protein as the ortholog in plant mitochondria of the bacterial CcmA required for cytochrome c maturation. The transporter that involves AtCCMA defines a new category of eukaryotic ABC proteins because its transmembrane and nucleotide binding domains are encoded by separate genomes.

Highlights

JULY 20, 2007 VOLUME 282 NUMBER 29 transporters are actively transported using ATP hydrolysis as energy source
In this work we show that NAP10 is a mitochondrial protein, which has kept the topology of its bacterial counterpart CcmA and has characteristics of the nucleotide binding domains (NBD) of an ATP binding cassette (ABC) transporter
Contrary to the mitochondrial ABC transporters described so far, which belong to the full or half-transporter types [25], the plant ABC transporter involved in c-type cytochrome maturation makes a novel class of organellar ABC transporter since its transmembrane domains (TMD) are encoded on the mitochondrial genome and its NBDs are encoded by the nuclear gene NAP10

Summary

Introduction

JULY 20, 2007 VOLUME 282 NUMBER 29 transporters are actively transported using ATP hydrolysis as energy source. In E. coli, ccm genes are organized in an operon starting with ccmA that encodes the nucleotide binding domain of an ABC transporter. In this work we show that NAP10 is a mitochondrial protein, which has kept the topology of its bacterial counterpart CcmA and has characteristics of the NBD of an ABC transporter.

Results

Conclusion