MUTATIONS IN THE TRPD GENE OF CORYNEBACTERIUM-GLUTAMICUM CONFER 5-METHYLTRYPTOPHAN RESISTANCE BY ENCODING A FEEDBACK-RESISTANT ANTHRANILATEPHOSPHORIBOSYLTRANSFERASE

The trpD gene from tryptophan-hyperproducing Corynebacterium glutamicu m ATCC 21850 was isolated on the basis of its ability to confer resist ance to 5-methyltryptophan on wild-type C. glutamicum AS019. Comparati ve sequence analysis of the genes from the wild-type AS019 and ATCC 21 850 trpD genes revealed two amino acid substitutions at the protein le vel. Further analysis demonstrated that the trpD gene product from ATC C 21850, anthranilate phosphoribosyltransferase, was more resistant to feedback inhibition by either tryptophan or 5-methyltryptophan than i ts wild-type counterpart. It is proposed that phosphoribosyltransferas e insensitivity to tryptophan in ATCC 21850 contributes to an elevated level of tryptophan biosynthesis.