Isolation and characterization of the structural gene encoding elongation factor 3

The unique yeast translational factor EF-3 participates in the elongation cycle by stimulating the function of EF-1 alpha in binding aminoacyl-tRNA to the ribosome. We have isolated the structural gene encoding EF-3 from the yeast Saccharomyces cerevisiae. The YEF3 gene is found in one copy per haploid genome and is essential for vegetative growth. DNA sequence analysis reveals that the YEF3 gene contains an open reading frame of 1044 codons. The deduced amino acid sequence has two repeats of a nucleotide-binding motif. Each of these repeats shows similarity to the nucleotide-binding motif of hydrophilic, membrane-associated ATPases including human multidrug resistant protein MDR. Factor 3 manifests ribosome-dependent ATP hydrolysis. Introduction of the YEF3 gene on a high copy number plasmid into yeast strains increases the ribosome-dependent ATPase activity and EF-3 protein levels by 3-5-fold. Yeast strains containing elevated EF-3 protein levels also exhibit increased sensitivity to the aminoglycoside antibiotics hygromycin and paromomycin. These drugs are known to increase translational errors. These observations suggest that EF-3 may affect translational accuracy.