PDBsum entry 1ab6

Chemotaxis

PDB id: 1ab6

Contents

Protein chains

125 a.a. *

Waters ×41

* Residue conservation analysis

PDB id:

1ab6

Name:

Chemotaxis

Title:

Structure of chey mutant f14n, v86t

Structure:

Chemotaxis protein chey. Chain: a, b. Synonym: chey. Engineered: yes. Mutation: yes

Source:

Escherichia coli. Organism_taxid: 562. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.20Å R-factor: 0.192 R-free: 0.280

Authors:

D.Wilcock,M.T.Pisabarro,E.Lopez-Hernandez,L.Serranno,M.Coll

Key ref:

D.Wilcock et al. (1998). Structure analysis of two CheY mutants: importance of the hydrogen-bond contribution to protein stability. Acta Crystallogr D Biol Crystallogr, 54, 378-385. PubMed id: 9761905

Date:

04-Feb-97 Release date: 04-Feb-98

Protein chains

P0AE67  (CHEY_ECOLI) -  Chemotaxis protein CheY from Escherichia coli (strain K12)

Seq: 129 a.a.

Struc: 125 a.a.*

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

Enzyme reactions

• Enzyme class: E.C.?

Acta Crystallogr D Biol Crystallogr 54:378-385 (1998)

PubMed id: 9761905

Structure analysis of two CheY mutants: importance of the hydrogen-bond contribution to protein stability.

D.Wilcock, M.T.Pisabarro, E.López-Hernandez, L.Serrano, M.Coll.

ABSTRACT

The crystal structures of two double mutants (F14N/V21T and F14N/V86T) of the signal transduction protein CheY have been determined to a resolution of 2.4 and 2.2 A, respectively. The structures were solved by molecular replacement and refined to final R values of 18.4 and 19.2%, respectively. Together with urea-denaturation experiments the structures have been used to analyse the effects of mutations where hydrophobic residues are replaced by residues capable of establishing hydrogen bonds. The large increase in stabilization (-12.1 kJ mol-1) of the mutation Phe14Asn arises from two factors: a reverse hydrophobic effect and the formation of a good N-cap at alpha-helix 1. In addition, a forward-backward hydrogen-bonding pattern, resembling an N-capping box and involving Asn14 and Arg18, has been found. The two Val to Thr mutations at the hydrophobic core have different thermodynamic effects: the mutation Val21Thr does not affect the stability of the protein while the mutation Val86Thr causes a small destabilization of 1.7 kJ mol-1. At site 21 a backward side chain-to-backbone hydrogen bond is formed inside alpha-helix 1 with the carbonyl O atom of the i - 4 residue without movement of the mutated side chain. The destabilizing effect of introducing a polar group in the core is efficiently compensated for by the formation of an extra hydrogen bond. At site 86 the new Ogamma atom escapes from the hydrophobic environment by a chi1 rotation into an adjacent hydrophilic cavity to form a new hydrogen bond. In this case the isosteric Val to Thr substitution is disruptive but the loss in stabilization energy is partly compensated by the formation of a hydrogen bond. The two crystal structures described in this work underline the significance of the hydrogen-bond component to protein stability.