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Eukaryotic Cell, March 2006, p. 568-578, Vol. 5, No. 3
1535-9778/06/$08.00+0     doi:10.1128/EC.5.3.568-578.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Mutational Analysis of the Saccharomyces cerevisiae Cytochrome c Oxidase Assembly Protein Cox11p

Graham S. Banting and D. Moira Glerum*

Department of Medical Genetics, University of Alberta, Edmonton, Alberta T6G 2H7, Canada

Received 31 October 2005/ Accepted 16 January 2006

Cox11p is an integral protein of the inner mitochondrial membrane that is essential for cytochrome c oxidase assembly. The bulk of the protein is located in the intermembrane space and displays high levels of evolutionary conservation. We have analyzed a collection of site-directed and random cox11 mutants in an effort to further define essential portions of the molecule. Of the alleles studied, more than half had no apparent effect on Cox11p function. Among the respiration deficiency-encoding alleles, we identified three distinct phenotypes, which included a set of mutants with a misassembled or partially assembled cytochrome oxidase, as indicated by a blue-shifted cytochrome aa3 peak. In addition to the shifted spectral signal, these mutants also display a specific reduction in the levels of subunit 1 (Cox1p). Two of these mutations are likely to occlude a surface pocket behind the copper-binding domain in Cox11p, based on analogy with the Sinorhizobium meliloti Cox11 solution structure, thereby suggesting that this pocket is crucial for Cox11p function. Sequential deletions of the matrix portion of Cox11p suggest that this domain is not functional beyond the residues involved in mitochondrial targeting and membrane insertion. In addition, our studies indicate that {Delta}cox11, like {Delta}sco1, displays a specific hypersensitivity to hydrogen peroxide. Our studies provide the first evidence at the level of the cytochrome oxidase holoenzyme that Cox1p is the in vivo target for Cox11p and suggest that Cox11p may also have a role in the response to hydrogen peroxide exposure.

* Corresponding author. Mailing address: Department of Medical Genetics, University of Alberta, 8-33 Medical Sciences Building, Edmonton, Alberta T6G 2H7, Canada. Phone: (780) 492-4563. Fax: (780) 492-1998. E-mail: moira.glerum{at}ualberta.ca.

Eukaryotic Cell, March 2006, p. 568-578, Vol. 5, No. 3
1535-9778/06/$08.00+0     doi:10.1128/EC.5.3.568-578.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



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