title: Structure and function of MRP20 and MRP49, the nuclear genes for two proteins of the 54 S subunit of the yeast mitochondrial ribosome.
abstract: MRP20 and MRP49 are proteins of the large subunit of the mitochondrial ribosome in Saccharomyces cerevisiae. Their genes were identified through immunological screening of a genomic library in the expression vector lambda gt11. Nucleotide sequencing revealed that MRP49 is tightly linked to TPK3 and encodes a 16-kDa, basic protein with no significant relatedness to any other known protein. MRP20 specifies a 263-amino-acid polypeptide with sequence similarity to members of the L23 family of ribosomal proteins. The levels of the mRNAs and proteins for both MRP20 and MRP49 were regulated in response to carbon source. In [rho0] strains lacking mitochondrial rRNA, the levels of the two proteins were reduced severalfold, presumably because the unassembled proteins are unstable. Null mutants of MRP20 converted to [rho-] or [rho0], a characteristic phenotype of mutations in essential genes for mitochondrial translation. Inactivation of MRP49 caused a cold-sensitive respiration-deficient phenotype, indicating that MRP49 is not an essential ribosomal protein. The mrp49 mutants were defective in the assembly of stable 54 S ribosomal subunits at the nonpermissive temperature. With the results presented here, there are now published sequences for 14 yeast mitochondrial ribosomal proteins, only five of which bear discernable relationships to eubacterial ribosomal proteins.
authors.affiliation: Department of Biochemistry, University of Massachusetts, Amherst 01003.
authors.forename: K
authors.initials: K
authors.lastname: Fearon
authors.forename: T L
authors.initials: TL
authors.lastname: Mason
mesh_terms: D000595:Amino Acid Sequence; D015139:Blotting, Southern; D002467:Cell Nucleus / Q000502:physiology; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000235:genetics / Q000302:isolation & purification; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D015698:Genomic Library; D046911:Macromolecular Substances; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D015183:Restriction Mapping; D012269:Ribosomal Proteins / Q000235:genetics*; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004271:DNA, Fungal; C073478:MRP20 protein, S cerevisiae; C073480:MRP49 protein, S cerevisiae; D046911:Macromolecular Substances; D024101:Mitochondrial Proteins; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins