2RLN

THERMODYNAMIC AND STRUCTURAL CONSEQUENCES OF CHANGING A SULPHUR ATOM TO A METHYLENE GROUP IN THE M13NLE MUTATION IN RIBONUCLEASE S

Summary for 2RLN

• Entry DOI: 10.2210/pdb2rln/pdb
• Descriptor: RIBONUCLEASE, RIBONUCLEASE S (S-PROTEIN), SULFATE ION, ... (4 entities in total)
• Functional Keywords: hydrolase(phosphoric diester, rna)
• Biological source: Bos taurus (cattle)
• Total number of polymer chains: 2
• Total formula weight: 13802.37

Authors

Ratnaparkhi, G.,Varadarajan, R. (deposition date: 1994-07-11, release date: 1994-11-01, Last modification date: 2024-10-09)

Primary citation

Thomson, J.,Ratnaparkhi, G.S.,Varadarajan, R.,Sturtevant, J.M.,Richards, F.M.
Thermodynamic and structural consequences of changing a sulfur atom to a methylene group in the M13Nle mutation in ribonuclease-S.
Biochemistry, 33:8587-8593, 1994

PubMed Abstract: 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)

PubMed: 8031793
DOI: 10.1021/bi00194a025

Experimental method

X-RAY DIFFRACTION (1.85 Å)