AN ADDITIONAL P-II IN ESCHERICHIA-COLI - A NEW REGULATORY PROTEIN IN THE GLUTAMINE-SYNTHETASE CASCADE

The P-II protein in the glutamine synthetase cascade transduces the nitrogen signal, as sensed by uridylyltransferase, both to the NRII/NRI two-component system and to adenylyltransferase, to regulate the activity of glutamine synthetase. Here we describe the amplification of a chromosomal DNA fragment from Escherichia coli which contains the sequence of a P-II homologue, The derived amino acid sequence of this DNA fragment is 67% identical to E. coli P-II. It contains the conserved tyrosine residue which is known to be the site of uridylylation in P-II. E. coli is the first organism in which two different P,, proteins have been detected,