2rln

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spinqualitylabelsall models 2rln, resolution 1.85Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

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 SO4 and NH2 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

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