PDBsum entry 4d4x

Electron transport

PDB id: 4d4x

Contents

Protein chain

126 a.a.

Ligands

HEC-_NO

Waters ×178

PDB id:

4d4x

Name:

Electron transport

Title:

Nitrosyl complex of the d121i variant of cytochromE C prime from alcaligenes xylosoxidans

Structure:

Cytochrome c'. Chain: a. Synonym: cytochromE C prime. Engineered: yes. Mutation: yes

Source:

Achromobacter xylosoxidans. Organism_taxid: 85698. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Resolution:

1.30Å R-factor: 0.171 R-free: 0.214

Authors:

D.D.Gahfoor,D.Kekilli,G.H.Abdullah,F.S.N.Dworkowski,H.G.Hassan, M.T.Wilson,M.A.Hough,R.W.Strange

Key ref:

D.D.Ghafoor et al. (2015). Hydrogen bonding of the dissociated histidine ligand is not required for formation of a proximal NO adduct in cytochrome c'. J Biol Inorg Chem, 20, 949-956. PubMed id: 26100643 DOI: 10.1007/s00775-015-1278-y

Date:

31-Oct-14 Release date: 09-Sep-15

Protein chain

P00138  (CYCP_ALCXX) -  Cytochrome c' from Alcaligenes xylosoxydans xylosoxydans

Seq: 127 a.a.

Struc: 127 a.a.*

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

DOI no: 10.1007/s00775-015-1278-y

J Biol Inorg Chem 20:949-956 (2015)

PubMed id: 26100643

Hydrogen bonding of the dissociated histidine ligand is not required for formation of a proximal NO adduct in cytochrome c'.

D.D.Ghafoor, D.Kekilli, G.H.Abdullah, F.S.Dworkowski, H.G.Hassan, M.T.Wilson, R.W.Strange, M.A.Hough.

ABSTRACT

Cytochromes c', that occur in methanotrophic, denitrifying and photosynthetic bacteria, form unusual proximal penta-coordinate NO complexes via a hexa-coordinate distal NO intermediate. Their NO binding properties are similar to those of the eukaryotic NO sensor, soluble guanylate cyclase, for which they provide a valuable structural model. Previous studies suggested that hydrogen bonding between the displaced proximal histidine (His120) ligand (following its dissociation from heme due to trans effects from the distally bound NO) and a conserved aspartate residue (Asp121) could play a key role in allowing proximal NO binding to occur. We have characterized three variants of Alcaligenes xylosoxidans cytochrome c' (AXCP) where Asp121 has been replaced by Ala, Ile and Gln, respectively. In all variants, hydrogen bonding between residue 121 and His120 is abolished yet 5-coordinate proximal NO species are still formed. Our data therefore demonstrate that the His120-Asp121 bond is not essential for proximal NO binding although it likely provides an energy minimum for the displaced His ligand. All variants have altered proximal pocket structure relative to native AXCP.