Mutants of yeast initiating translation of iso-1-cytochrome c within a region spanning 37 nucleotides

Cell. 1980 May;20(1):215-22. doi: 10.1016/0092-8674(80)90249-4.


We used a specially constructed strain, cyc1-345, of the yeast Saccharomyces cerevisiae to isolate revertants that initiated translation of iso-1-cytochrome c at various sites along an extended region of the mRNA. Normal amounts of iso-1-cytochrome c occurred when translation initiated at the abnormal sites corresponding to amino acid positions -3, -2, 3 and 5, as well as the normal position -1; 20% of the normal amounts occurred when translation initiated at the abnormal position 9. These results with cyc1-345 revertants indicate that translation of iso-1-cytochrome c can initiate with the normal efficiency at any site within the region spanning 25 nucleotides. Furthermore, because the lower amount of the short iso-1-cytochrome c in the mutant initiating at position 9 may not necessarily reflect an inefficiency of translation, we believe that translation can initiate with normal or near-normal efficiencies at any site within a 37 nucleotide region, and presumably at any site preceding and following that of the normal initiation codon. These results establish that there is no absolute requirement for a particular sequence 5' to the initiation codon, and are consistent with our previous suggestion that translation starts at the AUG codon closest to the 5' end of the mRNA.

MeSH terms

  • Base Sequence
  • Codon
  • Cytochrome c Group / genetics*
  • Mutation
  • Peptide Chain Initiation, Translational
  • Protein Biosynthesis*
  • RNA, Messenger / genetics*
  • Saccharomyces cerevisiae / genetics*


  • Codon
  • Cytochrome c Group
  • RNA, Messenger