Affiliation:
1. Department of Biological Sciences, Stanford University, Stanford, California 94305
Abstract
The
trpD
gene specifies a polypeptide which has both glutamine amidotransferase and phosphoribosyl anthranilate (PRA) transferase activities. Deletions fusing segments of
trpD
to the gene preceding it in the operon,
trpE
, were selected in strains carrying various
trpD
point mutations. The selection procedure required both that a deletion enter
trpE
and that it restore the PRA transferase activity which the parent
trpD
point mutant lacked. Deletion mutants were found which had PRA transferase activity although the first third of
trpD
was deleted. The existence of the mutants proves that a terminal segment of
trpD
is sufficient to specify a polypeptide having PRA transferase activity. The location of the deletion end points on the genetic map of
trpD
defines the extent of the
trpD
segment required for PRA transferase activity. This segment did not overlap the initial region of
trpD
required to specify the glutamine amidotransferase function of the
trpD
polypeptide. These results support the hypothesis (M. Grieshaber and R. Bauerle, 1972; H. Zalkin and L. H. Hwang, 1971) that the bifunctional
trpD
polypeptide might have evolved by fusion of a gene specifying a glutamine amidotransferase with a gene directing PRA transferase synthesis.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
44 articles.
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