Determination of the NMR Structure of Gln25-ribonuclease T1

Biol Chem. 2003 Aug;384(8):1173-83. doi: 10.1515/BC.2003.130.

Abstract

Ribonuclease (RNase) T1 is a guanyloribonuclease, having two isozymes in nature, Gln25- and Lys25-RNase T1. Between these two isozymes, there is no difference in catalytic activity and three-dimensional structure; however, Lys25-RNase T1 is slightly more stable than Gln25-RNase T1. Recently, it has been suggested that the existence of a salt bridge between Lys25 and Asp29/Glu31 in Lys25-RNase T1 contributes to the stability. To elucidate the effects of the replacement of Lys25 with a Gln on the conformation and microenvironments of RNase T1 in detail, the three-dimensional solution structure of Gln25-RNase T1 was determined by simulated-annealing calculations. As a result, the topology of the overall folding was shown to be very similar to that of the Lys25-isozyme except for some differences. In particular, there were two differences in the property of torsion angles of the two disulfide bonds and the conformations of the residues 11-13, 63-66, and 92-93. With regard to the residues 11-13, the lack of the above-mentioned salt bridge in Gln25-RNase T1 was thought to induce the conformational difference of this segment as compared with the Lys25-isozyme. Furthermore, it was proposed that the perturbation of this segment might transfer to the residues 92-93 via the two disulfide bonds.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Catalysis
  • Disulfides / chemistry
  • Glutamates / chemistry
  • Glycine / chemistry*
  • Histidine / chemistry
  • Hydrogen-Ion Concentration
  • Lysine / chemistry
  • Magnetic Resonance Spectroscopy
  • Protein Conformation
  • Ribonuclease T1 / chemistry*
  • Structure-Activity Relationship

Substances

  • Disulfides
  • Glutamates
  • Histidine
  • Ribonuclease T1
  • Lysine
  • Glycine