THE YEAST NUCLEAR GENE MRP-L13 CODES FOR A PROTEIN OF THE LARGE SUBUNIT OF THE MITOCHONDRIAL RIBOSOME

The nuclear gene MRP-LIS of Saccharomyces cerevisiae, which codes for the mitochondrial ribosomal protein YmL13, has been cloned and charact erized. It is a single-copy gene residing on chromosome XI. Its nucleo tide sequence was found to be identical to that of the previously repo rted ORF YK105. A comparison of the predicted protein sequence of the MRP-L13 gene product and the actual N-terminal amino-acid sequence of the isolated YmL13 protein indicated that the mature protein is preced ed by a mitochondrial signal peptide of 86 amino-acid residues, which is the longest among all known mitochondrial ribosomal proteins of S. cerevisiae. No sequence similarity was found to any other ribosomal pr otein in the current databases. The transcription of MRP-L13 was found to be repressed in the presence of glucose. Its protein product is no t strictly essential for mitochondrial functions, but disruption of th e gene by insertion of LEU2 noticeably affected cellular growth on non -fermentable carbon sources.