PDBsum entry: 1fev

Hydrolase

PDB id: 1fev

Contents

Protein chains

15 a.a.

101 a.a. *

Ligands

SO4

Waters ×42

* Residue conservation analysis

PDB id:

1fev

Name:

Hydrolase

Title:

Crystal structure of the ala4aib mutation in rnase s

Structure:

S peptide. Chain: a. Engineered: yes. S protein. Chain: b. Synonym: rnase s. Ec: 3.1.27.5

Source:

Synthetic: yes. Other_details: s peptide is a 16 residue synthetic peptide with ala4aib replacement. Bos taurus. Cattle. Organism_taxid: 9913. Tissue: pancreas

Biol. unit:

Dimer (from PQS)

Resolution:

2.25Å R-factor: 0.191 R-free: 0.229

Authors:

G.S.Ratnaparkhi,R.Varadarajan

Key ref:

G.S.Ratnaparkhi et al. (2000). Structural and thermodynamic consequences of introducing alpha-aminoisobutyric acid in the S peptide of ribonuclease S. Protein Eng, 13, 697-702. PubMed id: 11112508 DOI: 10.1093/protein/13.10.697

Date:

23-Jul-00 Release date: 09-Aug-00

Protein chain

P61823  (RNAS1_BOVIN) -  Ribonuclease pancreatic

Seq: 150 a.a.

Struc: 15 a.a.*

Protein chain

P61823  (RNAS1_BOVIN) -  Ribonuclease pancreatic

Seq: 150 a.a.

Struc: 101 a.a.

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

Enzyme reactions

• Enzyme class: Chains A, B: E.C.3.1.27.5 - Pancreatic ribonuclease.
• Reaction: Endonucleolytic cleavage to nucleoside 3'-phosphates and 3'-phosphooligonucleotides ending in C-P or U-P with 2',3'-cyclic phosphate intermediates.

 Gene Ontology (GO) functional annotation 

• Biochemical function: nucleic acid binding (2 terms)

DOI no: 10.1093/protein/13.10.697

Protein Eng 13:697-702 (2000)

PubMed id: 11112508

Structural and thermodynamic consequences of introducing alpha-aminoisobutyric acid in the S peptide of ribonuclease S.

G.S.Ratnaparkhi, S.K.Awasthi, P.Rani, P.Balaram, R.Varadarajan.

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.