Mutations Altering Initiation of Translation of Yeast Iso-1-cytochrome c; Contrasts between the Eukaryotic and Prokaryotic Initiation Process

Abstract

INTRODUCTION
Although the yeast Saccharomyces cerevisiae is a eukaryotic organism that has a greater genetic complexity than bacteria, it shares many of the technical advantages that permit rapid progress in determining fundamental mechanisms of biological processes. One of the major impacts of yeast in molecular biology is its use for investigating processes that are particularly amenable to genetic analysis and that are different in prokaryotes and eukaryotes. A systematic analysis of mutational alterations at the end of the CYC1 gene in the yeast S. cerevisiae has revealed the nucleotide sequences that effect initiation of translation. The analysis of these findings led us to suggest that certain essential features of the translational process may be fundamentally different from the analogous features in Escherichia coli. Furthermore, we have suggested that these differences between yeast and E. coli reflect differences between eukaryotes and prokaryotes. These findings and conclusions concerning the initiation process are briefly reviewed in this paper.

MUTATIONS OF THE AUG INITIATION CODON
Protein analysis of mutationally altered forms of iso-1-cytochrome c, along with genetic analysis of the corresponding mutant strains, established that the primary structure of this mitochondrial protein is determined by the CYC1 gene (Sherman et al. 1966), which is located on the right arm of chromosome X (Lawrence et al. 1975). Over 400 independently derived cyc1 mutants that lack iso-1-cytochrome c or that contain nonfunctional iso-1-cytochrome c have been isolated by one of three following procedures: (1) a spectroscopic scanning procedure (Sherman 1964), (2) a benzidine staining procedure (Sherman...