Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.3 (RNase T1)
 1,228 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have used NMR methods to characterize the structure and dynamics of ribonuclease Sa in solution. The solution structure of RNase Sa was obtained using the distance constraints provided by 2,276 NOEs and the C6-C96 disulfide bond. The 40 resulting structures are well determined; their mean pairwise RMSD is 0.76 A (backbone) and 1.26 A (heavy atoms). The solution structures are similar to previously determined crystal structures, especially in the secondary structure, but exhibit new features: the loop composed of Pro 45 to Ser 48 adopts distinct conformations and the rings of tyrosines 51, 52, and 55 have reduced flipping rates. Amide protons with greatly reduced exchange rates are found predominantly in interior beta-strands and the alpha-helix, but also in the external 3/10 helix and edge beta-strand linked by the disulfide bond. Analysis of (15)N relaxation experiments (R1, R2, and NOE) at 600 MHz revealed five segments, consisting of residues 1-5, 28-31, 46-50, 60-65, 74-77, retaining flexibility in solution. The change in conformation entropy for RNase SA folding is smaller than previously believed, since the native protein is more flexible in solution than in a crystal.
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PMID:Solution structure and dynamics of ribonuclease Sa. 1145 93

A structural characterization of bound water molecules in ribonuclease T1 (RNase T1) was carried out by nuclear magnetic resonance spectroscopy and molecular dynamics simulation. Amide protons of residues Trp59, Leu62, Tyr68 and Phe100 were found to cross-relax with protons of bound waters. Molecular dynamics simulations of the 120 water molecules observed in the free form of the crystal structure indicate that these amide protons donate hydrogen bonds to the less mobile water molecules. Hydrogen-bonded chains of the water molecules that are identified in the simulation study are located in the hairpin-like loop of RNase T1, comprising residues 62 to 76. The temperature factors of the observed water molecules in the crystal structure are very low, indicating that these bound waters are intrinsic components of RNase T1.
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PMID:Computational and NMR analyses for the identification of bound water molecules in ribonuclease T1. 1552 6

The conformational stability of ribonuclease Sa (RNase Sa) has been measured at the per-residue level by NMR-monitored hydrogen exchange at pH* 5.5 and 30 degrees C. In these conditions, the exchange mechanism was found to be EXII. The conformational stability calculated from the slowest exchanging amide groups was found to be 8.8 kcal/mol, in close agreement with values determined by spectroscopic methods. RNase Sa is curiously rich in acidic residues (pI = 3.5) with most basic residues being concentrated in the active-site cleft. The effects of dissolved salts on the stability of RNase Sa was studied by thermal denaturation experiments in NaCl and GdmCl and by comparing hydrogen exchange rates in 0.25 M NaCl to water. The protein was found to be stabilized by salt, with the magnitude of the stabilization being influenced by the solvent exposure and local charge environment at individual amide groups. Amide hydrogen exchange was also measured in 0.25, 0.50, 0.75, and 1.00 M GdmCl to characterize the unfolding events that permit exchange. In contrast to other microbial ribonucleases studied to date, the most protected, globally exchanging amides in RNase Sa lie not chiefly in the central beta strands but in the 3/10 helix and an exterior beta strand. These structural elements are near the Cys7-Cys96 disulfide bond.
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PMID:Ribonuclease Sa conformational stability studied by NMR-monitored hydrogen exchange. 1590 79