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J. Biol. Chem., Vol. 283, Issue 3, 1472-1479, January 18, 2008

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The Pentatricopeptide Repeats Present in Pet309 Are Necessary for Translation but Not for Stability of the Mitochondrial COX1 mRNA in Yeast^*

From the Departamento de Bioquímica, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Apartado postal 70-243, Mexico City 04510, Mexico

Pet309 is a protein essential for respiratory growth. It is involved in translation of the yeast mitochondrial COX1 gene, which encodes subunit I of the cytochrome c oxidase. Pet309 is also involved in stabilization of the COX1 mRNA. Mutations in a similar human protein, Lrp130, are associated with Leigh syndrome, where cytochrome c oxidase activity is affected. The sequence of Pet309 reveals the presence of at least seven pentatricopeptide repeats (PPRs) located in tandem in the central portion of the protein. Proteins containing PPR motifs are present in mitochondria and chloroplasts and are in general involved in RNA metabolism. Despite the increasing number of proteins from this family found to play essential roles in mitochondria and chloroplasts, little is understood about the mechanism of action of the PPR domains present in these proteins. In a series of in vivo analyses we constructed a pet309 mutant lacking the PPR motifs. Although the stability of the COX1 mRNA was not affected, synthesis of Cox1 was abolished. The deletion of one PPR motif at a time showed that all the PPR motifs are required for COX1 mRNA translation and respiratory growth. Mutations of basic residues in PPR3 caused reduced respiratory growth. According to a molecular model, these residues are facing a central cavity that could be involved in mRNA-binding activity, forming a possible path for this molecule on Pet309. Our results show that the RNA metabolism function of Pet309 is found in at least two separate domains of the protein.

Received for publication, October 10, 2007 , and in revised form, November 21, 2007.

^* This work was supported by the Consejo Nacional de Ciencia y Tecnologia (Grant 47514), Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica, Universidad Nacional Autónoma de México (Grants IN201805 and IN200507). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed. Tel.: 52-55-5622-5662; Fax: 52-55-5622-5630; E-mail: xperez{at}ifc.unam.mx.

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