PDBsum entry 1ytc

Electron transport

PDB id: 1ytc

Contents

Protein chain

112 a.a. *

Ligands

SO4

HEC

Waters ×116

* Residue conservation analysis

PDB id:

1ytc

Name:

Electron transport

Title:

Thermodynamic cycles as probes of structure-function relationships in unfolded proteins

Structure:

Yeast iso-2 cytochromE C. Chain: a. Engineered: yes. Mutation: yes. Other_details: reduced state of heme

Source:

Saccharomyces cerevisiae. Baker's yeast. Organism_taxid: 4932. Expressed in: escherichia coli. Expression_system_taxid: 562

Resolution:

1.80Å R-factor: 0.162

Authors:

Y.Luo,G.D.Brayer

Key ref:

W.A.McGee et al. (1996). Thermodynamic cycles as probes of structure in unfolded proteins. Biochemistry, 35, 1995-2007. PubMed id: 8639684 DOI: 10.1021/bi951228f

Date:

03-Jul-95 Release date: 08-Mar-96

Protein chain

P00045  (CYC7_YEAST) -  Cytochrome c isoform 2 from Saccharomyces cerevisiae (strain ATCC 204508 / S288c)

Seq: 113 a.a.

Struc: 112 a.a.*

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

DOI no: 10.1021/bi951228f

Biochemistry 35:1995-2007 (1996)

PubMed id: 8639684

Thermodynamic cycles as probes of structure in unfolded proteins.

W.A.McGee, F.I.Rosell, J.R.Liggins, S.Rodriguez-Ghidarpour, Y.Luo, J.Chen, G.D.Brayer, A.G.Mauk, B.T.Nall.

ABSTRACT

The relationship between structure and stability has been investigated for the folded forms and the unfolded forms of iso-2 cytochrome c and a variant protein with a stability-enhancing mutation, N52I iso-2. Differential scanning calorimetry has been used to measure the reversible unfolding transitions for the proteins in both heme oxidation states. Reduction potentials have been measured as a function of temperature for the folded forms of the proteins. The combination of measurements of thermal stability and reduction potential gives three sides of a thermodynamic cycle and allows prediction of the reduction potential of the thermally unfolded state. The free energies of electron binding for the thermally unfolded proteins differ from those expected for a fully unfolded protein, suggesting that residual structure modulates the reduction potential. At temperatures near 50 degrees C the N52I mutation has a small but significant effect on oxidation state-sensitive structure in the thermally unfolded protein. Inspection of the high-resolution X-ray crystallographic structures of iso-2 and N52I iso-2 shows that the effects of the N52I mutation and oxidation state on native protein stability are correlated with changes in the mobility of specific polypeptide chain segments and with altered hydrogen bonding involving a conserved water molecule. However, there is no clear explanation of oxidation state or mutation-induced differences in stability of the proteins in terms of observed changes in structure and mobility of the folded forms of the proteins alone.