Cloning and characterization of the gene coding for cytoplasmic seryl-tRNA synthetase from Saccharomyces cerevisiae.

We have screened a Saccharomyces cerevisiae expression library with antibodies against seryl-tRNA synthetase (SerRS) from baker's yeast. In this way we obtained clones which contain serS, the structural gene for seryl-tRNA synthetase. Genomic Southern blots show that the serS gene resides on a 5.0 kb SalI fragment. Nucleotide sequence analysis of the genes revealed a single open reading frame from which we deduced the amino acid sequence of the enzyme consistent with that of two peptides isolated from SerRS. The enzyme is comprised of 462 amino acids consistent with earlier determinations of its molecular weight. The codon usage of serS is typical of abundant yeast proteins. Nuclease S1 analysis of serS mRNA defined the RNA initiation site 20-40 bases downstream from an AT rich sequence containing the TATA box and 21-39 nucleotides upstream of the translation initiation codon. Yeast strains transformed with the cloned gene overproduce seryl-tRNA synthetase in vivo.