PDBsum entry 1e7o

Structural protein

PDB id: 1e7o

Contents

Protein chain

59 a.a. *

Ligands

GOL

Waters ×20

* Residue conservation analysis

PDB id:

1e7o

Name:

Structural protein

Title:

A-spectrin sh3 domain a11v, v23l, m25v, v44i, v58l mutations

Structure:

Spectrin alpha chain. Chain: a. Fragment: sh3-domain, residues 965-1025. Synonym: fodrin alpha chain, spectrin, non-erythroid alpha chain. Engineered: yes. Mutation: yes

Source:

Gallus gallus. Chicken. Organism_taxid: 9031. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Resolution:

3.20Å R-factor: 0.234 R-free: 0.237

Authors:

M.C.Vega,L.Serrano

Key ref:

E.S.Cobos et al. (2003). A thermodynamic and kinetic analysis of the folding pathway of an SH3 domain entropically stabilised by a redesigned hydrophobic core. J Mol Biol, 328, 221-233. PubMed id: 12684010 DOI: 10.1016/S0022-2836(03)00273-0

Date:

31-Aug-00 Release date: 21-May-03

Protein chain

P07751  (SPTN1_CHICK) -  Spectrin alpha chain, non-erythrocytic 1 from Gallus gallus

Seq: 2477 a.a.

Struc: 59 a.a.*

* PDB and UniProt seqs differ at 5 residue positions (black crosses)

DOI no: 10.1016/S0022-2836(03)00273-0

J Mol Biol 328:221-233 (2003)

PubMed id: 12684010

A thermodynamic and kinetic analysis of the folding pathway of an SH3 domain entropically stabilised by a redesigned hydrophobic core.

E.S.Cobos, V.V.Filimonov, M.C.Vega, P.L.Mateo, L.Serrano, J.C.Martínez.

ABSTRACT

The folding thermodynamics and kinetics of the alpha-spectrin SH3 domain with a redesigned hydrophobic core have been studied. The introduction of five replacements, A11V, V23L, M25V, V44I and V58L, resulted in an increase of 16% in the overall volume of the side-chains forming the hydrophobic core but caused no remarkable changes to the positions of the backbone atoms. Judging by the scanning calorimetry data, the increased stability of the folded structure of the new SH3-variant is caused by entropic factors, since the changes in heat capacity and enthalpy upon the unfolding of the wild-type and mutant proteins were identical at 298 K. It appears that the design process resulted in an increase in burying both the hydrophobic and hydrophilic surfaces, which resulted in a compensatory effect upon the changes in heat capacity and enthalpy. Kinetic analysis shows that both the folding and unfolding rate constants are higher for the new variant, suggesting that its transition state becomes more stable compared to the folded and unfolded states. The phi(double dagger-U) values found for a number of side-chains are slightly lower than those of the wild-type protein, indicating that although the transition state ensemble (TSE) did not change overall, it has moved towards a more denatured conformation, in accordance with Hammond's postulate. Thus, the acceleration of the folding-unfolding reactions is caused mainly by an improvement in the specific and/or non-specific hydrophobic interactions within the TSE rather than by changes in the contact order. Experimental evidence showing that the TSE changes globally according to its hydrophobic content suggests that hydrophobicity may modulate the kinetic behaviour and also the folding pathway of a protein.

Selected figure(s)

Figure 1.
Figure 1. The positions of the mutations in the 3D- scheme of the SH3 polypeptide chain. The side-chains, shown in grey, correspond to the replacements within the hydrophobic core that change WT into Best5-I25V. Alanine and glycine point mutations (D48G among them) are denoted in blue and magenta, respectively. The C-terminal is marked in yellow.

Figure 2.
Figure 2. (A) Stereo view of the backbone-superposition of the WT (blue) and Best5-I25V (red) variants of spectrin SH3. (B) Local confor- mational change related to the Lys26-Asp29 hydrogen bond. As an illustration we show both the side-chains and the experimental electron density in the regions of interest. (C). Local conformational change related to the Glu17-Arg49 salt bridge (green dotted line).

The above figures are reprinted by permission from Elsevier: J Mol Biol (2003, 328, 221-233) copyright 2003.

Figures were selected by an automated process.