RESUMO
Genomic DNA containing a third yeast glyceraldehyde-3-phosphate dehydrogenase structural gene has been isolated on a bacterial plasmid designated pgap11. The complete nucleotide sequence of this structural gene was determined. The gene contains no intervening sequences, codon usage is highly biased, and the nucleotide sequence of the coding portion of this gene is 90% homologous to the other two glyceraldehyde-3-phosphate dehydrogenase genes (Holland, J. P., and Holland, M. J. (1980) J. Biol. Chem. 255, 2596-2605). Based on the extent of nucleotide sequence divergence among the three glyceraldehyde-3-phosphate dehydrogenase genes, it is likely that they arose as a consequence of two duplication events and the gene contained on the hybrid plasmid designated pgap11 is a product of the first duplication event. All three structural genes share extensive nucleotide sequence homology in the 5'-noncoding regions adjacent to the three respective translational initiation codons. The gene contained on pgap11 is not homologous to the others downstream from the respective translational termination codon, however. The 5' termini of messenger RNAs synthesized from the three glyceraldehyde-3-phosphate dehydrogenase and two yeast enolase genes have been mapped to sites ranging from 36 to 82 nucleotides upstream from the respective translational initiation codons. In each case the 5' terminus of the mRNA maps to a region of strong nucleotide sequence homology which is shared by all five structural genes. These latter data confirm that all five structural genes are expressed during vegetative cell growth and further support the hypothesis that a portion of the 5'-noncoding flanking region of the yeast glyceraldehyde-3-phosphate dehydrogenase and enolase genes evolved from a common precursor sequence.
