Sequential Processing of a Mitochondrial Tandem Protein: Insights into Protein Import in Schizosaccharomyces pombe

Authors

Oleh Khalimonchuk, University of Nebraska-LincolnFollow
Martin Ott, Universität München
Soledad Funes, Universität München
Kai Ostermann, Technische Universität Dresden
Gerhard Rödel, Technische Universität Dresden
Johannes M. Herrmann, Universität München

Document Type

Article

Date of this Version

2006

Citation

EUKARYOTIC CELL, July 2006, p. 997–1006, Vol. 5, No. 7

Comments

Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Abstract

The sequencing of the genome of Schizosaccharomyces pombe revealed the presence of a number of genes encoding tandem proteins, some of which are mitochondrial components. One of these proteins (pre-Rsm22- Cox11) consists of a fusion of Rsm22, a component of the mitochondrial ribosome, and Cox11, a factor required for copper insertion into cytochrome oxidase. Since in Saccharomyces cerevisiae, Cox11 is physically attached to the mitochondrial ribosome, it was suggested that the tandem organization of Rsm22-Cox11 is used to covalently tie the mitochondrial ribosome to Cox11 in S. pombe. We report here that pre-Rsm22-Cox11 is matured in two subsequent processing events. First, the mitochondrial presequence is removed. At a later stage of the import process, the Rsm22 and Cox11 domains are separated by cleavage of the mitochondrial processing peptidase at an internal processing site. In vivo data obtained using a tagged version of pre-Rsm22- Cox11 confirmed the proteolytic separation of Cox11 from the Rsm22 domain. Hence, the tandem organization of pre-Rsm22-Cox11 does not give rise to a persistent fusion protein but rather might be used to increase the import efficiency of Cox11 and/or to coordinate expression levels of Rsm22 and Cox11 in S. pombe.