Summary: The gene encoding the bifunctional P-protein (chorismate mutase: prephenate dehydratase) was cloned from and sequenced. This is the first gene of phenylalanine biosynthesis to be cloned and sequenced from . The gene was expressed in , allowing complementation of an auxotroph. The enzymic and physical properties of the P-protein from a recombinant auxotroph expressing the gene were identical to those of the native enzyme from . The nucleotide sequence of the gene was 1095 base pairs in length, predicting a 365-residue protein product with an of 40844. Codon usage in the gene was similar to that of but unusual in that cytosine and guanine were used at nearly equal frequencies in the third codon position. The deduced P-protein product showed sequence homology with peptide sequences of the P-protein, the N-terminal portion of the T-protein (chorismate mutase: prephenate dehydrogenase), and the monofunctional prephenate dehydratases of and . A narrow range of values (26-35%) for amino acid matches revealed by pairwise alignments of monofunctional and bifunctional proteins possessing activity for prephenate dehydratase suggests that extensive divergence has occurred between even the nearest phylogenetic lineages.


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