Protein structure and dynamics were investigated in solution and in the crystalline state using nuclear magnetic resonance spectroscopy in order to understand function. Studies were carried out on: (a) staphylococcal nuclease, a calcium dependent phosphodiesterase, (b) IIIGlc the phospho- carrier regulatory protein of the bacterial PTS system, and (c) transforming growth factor ~1, TGF-beta1. A. S. nuclease Using three dimensional NMR methods, we have shown that deletion of six residues at the active site of the protein transforms a disordered omega loop into an ordered tight turn, thus explaining the enhanced stability of the mutant protein. The NMR work further shows that mutating residues in the turn affects catalytic function by perturbing the local conformation at the active site. Dynamic studies of the wild type protein show that leucine sidechains exhibit significant flexibility in spite of the fact that they are buried within the hydrophobic core of the protein. B. IIIGlc During the past year, complete signal assignments have been obtained for the 168 residue protein, and the secondary and teritary structures have been elucidated in solution. This is the largest protein that has been assigned without the aid of a crystal structure. Subsequent to the NMR work, a crystal structure has become available, which is fully consistent with the solution structure obtained by NMR. C. TGF-beta1 Optimal conditions for obtaining high resolution NMR spectra of TGF-beta1 have been determined. A fully 15 N enriched sample has been obtained from transfected CHO cells. Work is underway to fully assign the signals of the protein. These assignments will enable us to fully interpret the 3D-NOESY spectrum that we have obtained and thereby allow us to work out the secondary structure of the protein.
