Functional analysis of homologs of translation initiation factor 2gamma in yeast.
The gamma subunit of eukaryotic translation initiation factor 2 is an EF-Tu-like protein that plays an essential role in protein synthesis. We have isolated an eIF-2gamma homolog from the fission yeast Schizosaccharomyces pombe that complements a gcd11 null allele in Saccharomyces cerevisiae. GCD11 is an essential gene that encodes S. cerevisiae eIF-2gamma. Comparison among three eIF-2gamma homologs from humans, S. cerevisiae, and S. pombe, and a putative Drosophila homolog, reveals the presence of a domain N-terminal to the GTP-binding (G) domain that varies in length (relative to EF-Tu) from 12 residues in S. pombe to 89 residues in S. cerevisiae. In S. cerevisiae, these sequences are not essential for function. However, unlike a deletion, a missense mutation in this domain confers a slow growth phenotype and constitutively derepresses expression of the GCN4 transcriptional activator. The eIF-2gamma homologs also contain a partially conserved 35-37 amino acid insertion in the G domain that is absent from EF-Tu and other G proteins. Unlike the variable N-terminal domain, these residues are required for the essential function of eIF-2gamma.
Erickson
F L
FL
University of Texas at Dallas, Department of Molecular and Cell Biology, Richardson 75083-0688, USA.
Harding
L D
LD
Dorris
D R
DR
Hannig
E M
EM
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003545:Cysteine / Q000502:physiology; D018076:DNA, Complementary / Q000302:isolation & purification; D004268:DNA-Binding Proteins; D004330:Drosophila; D015852:Eukaryotic Initiation Factor-2 / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D011392:Proline / Q000502:physiology; D011494:Protein Kinases / Q000096:biosynthesis / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D015852:Eukaryotic Initiation Factor-2; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D011392:Proline; D011494:Protein Kinases; D003545:Cysteine