2rln
From Proteopedia
|
THERMODYNAMIC AND STRUCTURAL CONSEQUENCES OF CHANGING A SULPHUR ATOM TO A METHYLENE GROUP IN THE M13NLE MUTATION IN RIBONUCLEASE S
Overview
Two fragments of pancreatic ribonuclease A, a truncated version of S-peptide (residues 1-15) and S-protein (residues 21-124), combine to give a catalytically active complex. We have substituted the wild-type residue at position 13, methionine (Met), with norleucine (Nle), where the only covalent change is the replacement of the sulfur atom with a methylene group. The thermodynamic parameters associated with the binding of this variant to S-protein, determined by titration calorimetry in the temperature range 10-40 degrees C, are reported and compared to values previously reported [Varadarajan, R., Connelly, P. R., Sturtevant, J. M., & Richards, F. M. (1992) Biochemistry 31, 1421-1426] for other position 13 analogs. The differences in the free energy and enthalpy of binding between the Met and Nle peptides are 0.6 and 7.9 kcal/mol at 25 degrees C, respectively. These differences are slightly larger than, but comparable to, the differences in the values for the Met/Ile and Met/Leu pairs. The structure of the mutant complex was determined to 1.85 A resolution and refined to an R-factor of 17.4%. The structures of mutant and wild-type complexes are practically identical although the Nle side chain has a significantly higher average B-factor than the corresponding Met side chain. In contrast, the B-factors of the atoms of the cage of residues surrounding position 13 are all somewhat lower in the Nle variant than the Met wild-type.(ABSTRACT TRUNCATED AT 250 WORDS)
About this Structure
2RLN is a Single protein structure of sequence from Bos taurus with and as ligands. Active as Pancreatic ribonuclease, with EC number 3.1.27.5 Full crystallographic information is available from OCA.
Reference
Thermodynamic and structural consequences of changing a sulfur atom to a methylene group in the M13Nle mutation in ribonuclease-S., Thomson J, Ratnaparkhi GS, Varadarajan R, Sturtevant JM, Richards FM, Biochemistry. 1994 Jul 19;33(28):8587-93. PMID:8031793
Page seeded by OCA on Thu Feb 21 18:48:18 2008
