PDBsum entry 4aam

Oxidoreductase

PDB id: 4aam

Contents

Protein chain

324 a.a.

Ligands

HEC ×2

SO4 ×2

Metals

_CA

Waters ×320

PDB id:

4aam

Name:

Oxidoreductase

Title:

Maca wild-type mixed-valence

Structure:

Cytochrome c551 peroxidase. Chain: a. Fragment: residues 23-346. Synonym: cytochromE C peroxidase. Engineered: yes

Source:

Geobacter sulfurreducens. Organism_taxid: 243231. Strain: pca. Expressed in: escherichia coli. Expression_system_taxid: 469008. Expression_system_variant: star. Other_details: dsm

Resolution:

2.17Å R-factor: 0.166 R-free: 0.239

Authors:

J.Seidel

Key ref:

J.Seidel et al. (2012). MacA is a second cytochrome c peroxidase of Geobacter sulfurreducens. Biochemistry, 51, 2747-2756. PubMed id: 22417533

Date:

05-Dec-11 Release date: 17-Oct-12

Protein chain

Q74FY6  (Q74FY6_GEOSL) -  Cytochrome c peroxidase from Geobacter sulfurreducens (strain ATCC 51573 / DSM 12127 / PCA)

Seq: 346 a.a.

Struc: 324 a.a.

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 = HEC) matches with 95.45% similarity)

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

Added reference

Biochemistry 51:2747-2756 (2012)

PubMed id: 22417533

MacA is a second cytochrome c peroxidase of Geobacter sulfurreducens.

J.Seidel, M.Hoffmann, K.E.Ellis, A.Seidel, T.Spatzal, S.Gerhardt, S.J.Elliott, O.Einsle.

ABSTRACT

The metal-reducing δ-proteobacterium Geobacter sulfurreducens produces a large number of c-type cytochromes, many of which have been implicated in the transfer of electrons to insoluble metal oxides. Among these, the dihemic MacA was assigned a central role. Here we have produced G. sulfurreducens MacA by recombinant expression in Escherichia coli and have solved its three-dimensional structure in three different oxidation states. Sequence comparisons group MacA into the family of diheme cytochrome c peroxidases, and the protein indeed showed hydrogen peroxide reductase activity with ABTS(-2) as an electron donor. The observed K(M) was 38.5 ± 3.7 μM H(2)O(2) and v(max) was 0.78 ± 0.03 μmol of H(2)O(2)·min(-1)·mg(-1), resulting in a turnover number k(cat) = 0.46 · s(-1). In contrast, no Fe(III) reductase activity was observed. MacA was found to display electrochemical properties similar to other bacterial diheme peroxidases, in addition to the ability to electrochemically mediate electron transfer to the soluble cytochrome PpcA. Differences in activity between CcpA and MacA can be rationalized with structural variations in one of the three loop regions, loop 2, that undergoes conformational changes during reductive activation of the enzyme. This loop is adjacent to the active site heme and forms an open loop structure rather than a more rigid helix as in CcpA. For the activation of the protein, the loop has to displace the distal ligand to the active site heme, H93, in loop 1. A H93G variant showed an unexpected formation of a helix in loop 2 and disorder in loop 1, while a M297H variant that altered the properties of the electron transfer heme abolished reductive activation.