1FEV

CRYSTAL STRUCTURE OF THE ALA4AIB MUTATION IN RNASE S

Summary for 1FEV

• Entry DOI: 10.2210/pdb1fev/pdb
• Related: 1D5D 1D5E 1D5H 1RBH 1RNV
• Descriptor: S PEPTIDE, S PROTEIN, SULFATE ION, ... (4 entities in total)
• Functional Keywords: alpha aminoisobutyric acid, aib, hydrolase
• Biological source: Bos taurus (cattle); More
• Cellular location: Secreted: P61823 P61823
• Total number of polymer chains: 2
• Total formula weight: 13139.75

Authors

Ratnaparkhi, G.S.,Varadarajan, R. (deposition date: 2000-07-23, release date: 2000-08-09, Last modification date: 2021-11-03)

Primary citation

Ratnaparkhi, G.S.,Awasthi, S.K.,Rani, P.,Balaram, P.,Varadarajan, R.
Structural and thermodynamic consequences of introducing alpha-aminoisobutyric acid in the S peptide of ribonuclease S.
Protein Eng., 13:697-702, 2000

PubMed Abstract: 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.

PubMed: 11112508
DOI: 10.1093/protein/13.10.697

Experimental method

X-RAY DIFFRACTION (2.25 Å)