1FEV image
Deposition Date 2000-07-23
Release Date 2000-08-09
Last Version Date 2021-11-03
Entry Detail
PDB ID:
1FEV
Keywords:
Title:
CRYSTAL STRUCTURE OF THE ALA4AIB MUTATION IN RNASE S
Biological Source:
Source Organism:
(Taxon ID: )Bos taurus (Taxon ID: 9913)
Method Details:
Experimental Method:
Resolution:
2.25 Å
R-Value Free:
0.22
R-Value Work:
0.19
R-Value Observed:
0.19
Space Group:
P 31 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:S PEPTIDE
Gene (Uniprot):RNASE1
Chain IDs:A
Chain Length:15
Number of Molecules:1
Biological Source:
Polymer Type:polypeptide(L)
Molecule:S PROTEIN
Gene (Uniprot):RNASE1
Chain IDs:B
Chain Length:101
Number of Molecules:1
Biological Source:Bos taurus
Modified Residue
Compound ID Chain ID Parent Comp ID Details 2D Image
AIB A ALA ALPHA-AMINOISOBUTYRIC ACID
Ligand Molecules
Primary Citation
Structural and thermodynamic consequences of introducing alpha-aminoisobutyric acid in the S peptide of ribonuclease S.
Protein Eng. 13 697 702 (2000)
PMID: 11112508 DOI: 10.1093/protein/13.10.697

Abstact

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.

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Primary Citation of related structures