1fev
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(New page: 200px<br /><applet load="1fev" size="450" color="white" frame="true" align="right" spinBox="true" caption="1fev, resolution 2.25Å" /> '''CRYSTAL STRUCTURE OF...)
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Revision as of 12:44, 20 November 2007
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CRYSTAL STRUCTURE OF THE ALA4AIB MUTATION IN RNASE S
Overview
The S protein-S peptide interaction is a model system to study binding, thermodynamics in proteins. We substituted alanine at position 4 in S, peptide by alpha-aminoisobutyric acid (Aib) to investigate the effect of, this substitution on the conformation of free S peptide and on its binding, to S protein. The thermodynamic consequences of this replacement were, studied using isothermal titration calorimetry. The structures of the free, and complexed peptides were studied using circular dichroic spectroscopy, and X-ray crystallography, respectively. The alanine4Aib replacement, stabilizes the free S peptide helix and does not perturb the tertiary, structure of RNase S. Surprisingly, and in contrast to the wild-type S, peptide, the DeltaG degrees of binding of peptide to S pro, over the, temperature range 5-30 degrees C, is virtually independent of temperature., At 25 degrees C, the DeltaDeltaG degrees, DeltaDeltaH degrees, DeltaDeltaS, and DeltaDeltaCp of binding are 0.7 kcal/mol, 2.8 kcal/mol, 6 kcal/mol x K, and -60 kcal/mol x K, respectively. The positive value of DeltaDeltaS is, probably due to a decrease in the entropy of uncomplexed alanine4Aib, relative to the wild-type peptide. The positive value of DeltaDeltaH:, degrees is unexpected and is probably due to favorable interactions formed, in uncomplexed alanine4Aib. This study addresses the thermodynamic and, structural consequences of a replacement of alanine by Aib both in the, unfolded and complexed states in proteins.
About this Structure
1FEV is a Protein complex structure of sequences from Bos taurus with SO4 as ligand. Active as Pancreatic ribonuclease, with EC number 3.1.27.5 Full crystallographic information is available from OCA.
Reference
Structural and thermodynamic consequences of introducing alpha-aminoisobutyric acid in the S peptide of ribonuclease S., Ratnaparkhi GS, Awasthi SK, Rani P, Balaram P, Varadarajan R, Protein Eng. 2000 Oct;13(10):697-702. PMID:11112508
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