STRUCTURE OF THE ESCHERICHIA-COLI SIGNAL-TRANSDUCING PROTEIN P-II

Background: In Gram-negative proteobacteria, the nitrogen level in the cell is reflected by the uridylylation status of a key signal transdu cing protein, P-II. P-II modulates the activity of glutamine synthetas e (GS) through its interaction with adenylyl transferase and it repres ses the expression of GS by acting in concert with nitrogen regulatory protein II. Results: The three-dimensional structure of the Escherich ia coli P-II trimer has been determined at 2.7 Angstrom resolution. PI I shows a low level of structural similarity to a broad family of alph a/beta proteins and contains a double beta alpha beta motif. The P-II trimer contains three beta-sheets, each of which is composed of strand s from each of the three monomers. These are surrounded by six alpha-h elices. Conclusions: The structure of P-II suggests potential regions of interaction with other proteins and serves as an initial step in un derstanding its signal transducing role in nitrogen regulation.