The Escherichia coli bifunctional T-protein transforms chorismic acid to p-hydroxyphenylpyruvic acid in the L-tyrosine biosynthetic pathway. The 373 amino acid T-protein is a homodimer that exhibits chorismate mutase (CM) and prephenate dehydrogenase (PDH) activities, both of which are feedback-inhibited by tyrosine. Fifteen genes coding for the T-protein and various fragments thereof were constructed and successfully expressed in order to charac-terize theCM, PDHand regulatory domains.
