2bnh
From Proteopedia
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PORCINE RIBONUCLEASE INHIBITOR
Overview
We describe the mechanism of ribonuclease inhibition by ribonuclease, inhibitor, a protein built of leucine-rich repeats, based on the crystal, structure of the complex between the inhibitor and ribonuclease A. The, structure was determined by molecular replacement and refined to an Rcryst, of 19.4% at 2.5 A resolution. Ribonuclease A binds to the concave region, of the inhibitor protein comprising its parallel beta-sheet and loops. The, inhibitor covers the ribonuclease active site and directly contacts, several active-site residues. The inhibitor only partially mimics the, RNase-nucleotide interaction and does not utilize the p1 phosphate-binding, pocket of ribonuclease A, where a sulfate ion remains bound. The 2550 A2, of accessible surface area buried upon complex formation may be one of the, major contributors to the extremely tight association (Ki = 5.9 x 10(-14), M). The interaction is predominantly electrostatic; there is a high, chemical complementarity with 18 putative hydrogen bonds and salt links, but the shape complementarity is lower than in most other protein-protein, complexes. Ribonuclease inhibitor changes its conformation upon complex, formation; the conformational change is unusual in that it is a plastic, reorganization of the entire structure without any obvious hinge and, reflects the conformational flexibility of the structure of the inhibitor., There is a good agreement between the crystal structure and other, biochemical studies of the interaction. The structure suggests that the, conformational flexibility of RI and an unusually large contact area that, compensates for a lower degree of complementarity may be the principal, reasons for the ability of RI to potently inhibit diverse ribonucleases., However, the inhibition is lost with amphibian ribonucleases that have, substituted most residues corresponding to inhibitor-binding residues in, RNase A, and with bovine seminal ribonuclease that prevents inhibitor, binding by forming a dimer.
About this Structure
2BNH is a Single protein structure of sequence from Sus scrofa with ACE as ligand. This structure superseeds the now removed PDB entry 1BNH. Full crystallographic information is available from OCA.
Reference
Mechanism of ribonuclease inhibition by ribonuclease inhibitor protein based on the crystal structure of its complex with ribonuclease A., Kobe B, Deisenhofer J, J Mol Biol. 1996 Dec 20;264(5):1028-43. PMID:9000628
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