Active site of RNase: neutron diffraction study of a complex with uridine vanadate, a transition-state analog.
A complex of RNase A with a transition-state analog, uridine vanadate, has been studied by a combination of neutron and x-ray diffraction. The vanadium atom occupies the center of a distorted trigonal bipyramid, with the ribose oxygen O2' at the apical position. Contrary to expectations based on the straightforward interpretation of the known in-line mechanism of action of RNase, nitrogen NE2 of histidine-12 was found to form a hydrogen bond to the equatorial oxygen O8, while nitrogen NZ of lysine-41 makes a clear hydrogen bond to the apical oxygen O2'. Nitrogen ND1 of histidine-119 appears to be within a hydrogen-bond distance of the other apical oxygen, O7. Two other hydrogen bonds between the vanadate and the protein are made by nitrogen NE2 of glutamine-11 and by the amide nitrogen of phenylalanine-120. The observed geometry of the complex may necessitate reinterpretation of the mechanism of action of RNase.
D000818:Animals; D001665:Binding Sites; D004722:Endoribonucleases / Q000378:metabolism*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009502:Neutrons; D010179:Pancreas / Q000201:enzymology; D011487:Protein Conformation; D012259:Ribonuclease, Pancreatic; D013057:Spectrum Analysis; D014529:Uridine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014961:X-Ray Diffraction
C038271:uridine vanadate; D004722:Endoribonucleases; D012259:Ribonuclease, Pancreatic; D014529:Uridine