Analysis of exon and intron mutants in the cytochrome b mitochondrial gene of Saccharomyces cerevisiae.
The nucleotide changes present in a group of five cytochrome b mit- mutants were analyzed at the sequence level. Two single-base changes were found: one (M10-152) generated a nonsense codon in the first exon while the other (M8-181) created a missense substitution in the second exon. The other mutants all have multiple (three) substitutions that either resulted in a missense mutation in a coding region (M17-162) or else changed nucleotides in the last intron of the gene, so blocking its excision (M6-200 and M8-53). The synthesis of mitochondrial polypeptides and the steady state concentration of the complex-III subunits were examined. The Rieske protein and the core-4 and core-5 subunits were much reduced in all mutants. Consequently the overall stability of complex III is very sensitive even to amino-acid substitutions in the cytochrome b protein. Mutant M8-53 provides direct evidence for the proposed role of the P9.1 stem in the core structure of the group-I type last intron of this gene.
Bonjardim
C A
CA
Laboratório de Vírus, Depto. de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, MG, Brasil.
Pereira
L S
LS
Nobrega
F G
FG
D001059:Apoproteins / Q000235:genetics; D003062:Codon; D003573:Cytochrome b Group / Q000096:biosynthesis / Q000235:genetics*; D045303:Cytochromes b; D004272:DNA, Mitochondrial / Q000235:genetics*; D014450:Electron Transport Complex III / Q000096:biosynthesis / Q000235:genetics; D005091:Exons; D007438:Introns; D008928:Mitochondria / Q000378:metabolism; D009154:Mutation; D017354:Point Mutation; D012333:RNA, Messenger / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D001059:Apoproteins; D003062:Codon; D003573:Cytochrome b Group; D004272:DNA, Mitochondrial; D012333:RNA, Messenger; D045303:Cytochromes b; D014450:Electron Transport Complex III