ATPASE ACTIVITY OF TYRR, A TRANSCRIPTIONAL REGULATORY PROTEIN FOR SIGMA(70) RNA-POLYMERASE

The TyrR protein of Escherichia coli is the chief transcriptional regu lator of several genes essential for aromatic amino acid biosynthesis and transport. It was established in previous studies that this protei n binds ATP, that the TyrR . ATP complex has enhanced affinity for tyr osine, and that the susceptibility of the TyrR protein to hydrolysis b y trypsin is altered by ATP. Here we show that the TyrR protein has AT Pase activity, which is stimulated by tyrosine. In this respect the Ty rR protein resembles the transcriptional activator NtrC. The NtrC prot ein contains an internal polypeptide segment, 220 amino acid residues in length, with a high degree of identity to the TyrR protein, that co ntains the presumptive ATPase catalytic center.