PDBsum entry 1ccc

Oxidoreductase

PDB id: 1ccc

Contents

Protein chain

291 a.a. *

Ligands

HEM

Waters ×51

* Residue conservation analysis

PDB id:

1ccc

Name:

Oxidoreductase

Title:

The asp-his-fe triad of cytochromE C peroxidase controls the reduction potential, electronic structure, and coupling of the tryptophan free- radical to the heme

Structure:

CytochromE C peroxidase. Chain: a. Engineered: yes

Source:

Saccharomyces cerevisiae. Baker's yeast. Organism_taxid: 4932

Resolution:

2.00Å R-factor: 0.190

Authors:

D.B.Goodin,D.E.Mcree

Key ref:

D.B.Goodin and D.E.McRee (1993). The Asp-His-Fe triad of cytochrome c peroxidase controls the reduction potential, electronic structure, and coupling of the tryptophan free radical to the heme. Biochemistry, 32, 3313-3324. PubMed id: 8384877 DOI: 10.1021/bi00064a014

Date:

04-Jan-93 Release date: 31-Oct-93

Protein chain

P00431  (CCPR_YEAST) -  Cytochrome c peroxidase, mitochondrial from Saccharomyces cerevisiae (strain ATCC 204508 / S288c)

Seq: 361 a.a.

Struc: 291 a.a.*

* PDB and UniProt seqs differ at 3 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.1.11.1.5 - cytochrome-c peroxidase.
• Reaction: 2 Fe(II)-[cytochrome c] + H2O2 + 2 H⁺ = 2 Fe(III)-[cytochrome c] + 2 H2O
• Cofactor: Heme

Heme (Bound ligand (Het Group name = HEM) matches with 95.45% similarity)

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

Added reference

DOI no: 10.1021/bi00064a014

Biochemistry 32:3313-3324 (1993)

PubMed id: 8384877

The Asp-His-Fe triad of cytochrome c peroxidase controls the reduction potential, electronic structure, and coupling of the tryptophan free radical to the heme.

D.B.Goodin, D.E.McRee.

ABSTRACT

The buried charge of Asp-235 in cytochrome c peroxidase (CCP) forms an important hydrogen bond to the histidine ligand of the heme iron. The Asp-His-metal interaction, which is similar to the catalytic triad of serine proteases, is found at the active site of many metalloenzymes and is believed to modulate the character of histidine as a metal ligand. We have examined the influence of this interaction in CCP on the function, redox properties, and iron zero-field splitting in the native ferric state and its effect on the Trp-191 free radical site in the oxidized ES complex. Unlike D235A and D235N, the mutation D235E introduces very little perturbation in the X-ray crystal structure of the enzyme active site, with only minor changes in the geometry of the carboxylate-histidine interaction and no observable change at the Trp-191 free radical site. More significant effects are observed in the position of the helix containing residue Glu-235. However, the small change in hydrogen bond geometry is all that is necessary to (1) increase the reduction potential by 70 mV, (2) alter the anisotropy of the Trp-191 free radical EPR, (3) affect the activity and spin-state equilibrium, and (4) reduce the strength of the iron ligand field as measured by the zero-field splitting. The changes in the redox potential with substitution are correlated with the observed zero-field splitting, suggesting that redox control is exerted through the heme ligand by a combination of electrostatic and ligand field effects. The replacement of Asp-235 with Glu appears to result in a significantly weaker hydrogen bond in which the proton resides essentially with His-175. This hydrogen bond is nevertheless strong enough to prevent the reorientation of Trp-191 and the conversion to one of two low-spin states observed for D235A and D235N. The Asp-His-Fe interaction is therefore as important in defining the redox properties and imidazolate character of His-175 as has been proposed, yet its most important role in peroxidase function may be to correctly orient Trp-191 for efficient coupling of the free radical to the heme and to maintain a high-spin 5-coordinate heme center.