title: Conformation of 3'CMP bound to RNase A using TrNOESY.
abstract: The conditions for accurately determining distance constraints from TrNOESY data on a small ligand (3'CMP) bound to a small protein (RNase A, <14 kDa) are described. For small proteins, normal TrNOESY conditions of 10:1 ligand:protein or greater can lead to inaccurate structures for the ligand-bound conformation due to the contribution of the free ligand to the TrNOESY signals. By using two ligand:protein ratios (2:1 and 5:1), which give the same distance constraints, a conformation of 3'CMP bound to RNase A was determined (glycosidic torsion angle, chi=-166 degrees ; pseudorotational phase angle, 0 degrees < or = P < or =36 degrees ). Ligand-protein NOESY cross peaks were also observed and used to dock 3'CMP into the binding pocket of the apo-protein (7rsa). After energy minimization, the conformation of the 3'CMP:RNase A complex was similar to the X-ray structure (1 rpf) except that a C3'-endo conformation for the ribose ring (rather than C2'-exo conformation) was found in the TrNOESY structure.
authors.affiliation: National Cancer Institute at Frederick, Laboratory of Medical Chemistry, 376 Boyles Street, Building 376, Frederick, MD 21702, USA.
authors.forename: Yi-Chien
authors.initials: YC
authors.lastname: Lee
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Jackson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Jablonsky
authors.forename: Donald D
authors.initials: DD
authors.lastname: Muccio
mesh_terms: D003198:Computer Simulation; D003568:Cytidine Monophosphate / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D008968:Molecular Conformation; D012259:Ribonuclease, Pancreatic / Q000378:metabolism*
chemical_list: D012259:Ribonuclease, Pancreatic; D003568:Cytidine Monophosphate