PDBsum entry 4ccs

Unknown function

PDB id: 4ccs

Contents

Protein chain

226 a.a.

Ligands

MLT

EDO

Metals

_NA

Waters ×238

PDB id:

4ccs

Name:

Unknown function

Title:

The structure of cbix, the terminal enzyme for biosynthesis of siroheme in denitrifying bacteria

Structure:

Cbix. Chain: a. Engineered: yes

Source:

Paracoccus pantotrophus. Organism_taxid: 82367. Expressed in: escherichia coli. Expression_system_taxid: 511693. Expression_system_variant: codonplus.

Resolution:

1.90Å R-factor: 0.196 R-free: 0.237

Authors:

S.Bali,S.E.Rollauer,P.Roversi,E.Raux-Deery,S.M.Lea,M.J.Warren, S.J.Ferguson

Key ref:

S.Bali et al. (2014). Identification and characterization of the 'missing' terminal enzyme for siroheme biosynthesis in α-proteobacteria. Mol Microbiol, 92, 153-163. PubMed id: 24673795 DOI: 10.1111/mmi.12542

Date:

25-Oct-13 Release date: 09-Apr-14

Protein chain

A0A023GPI5  (A0A023GPI5_PARPN) -  CBIX from Paracoccus pantotrophus

Seq: 231 a.a.

Struc: 226 a.a.

DOI no: 10.1111/mmi.12542

Mol Microbiol 92:153-163 (2014)

PubMed id: 24673795

Identification and characterization of the 'missing' terminal enzyme for siroheme biosynthesis in α-proteobacteria.

S.Bali, S.Rollauer, P.Roversi, E.Raux-Deery, S.M.Lea, M.J.Warren, S.J.Ferguson.

ABSTRACT

It has recently been shown that the biosynthetic route for both the d1 -haem cofactor of dissimilatory cd1 nitrite reductases and haem, via the novel alternative-haem-synthesis pathway, involves siroheme as an intermediate, which was previously thought to occur only as a cofactor in assimilatory sulphite/nitrite reductases. In many denitrifiers (which require d1 -haem), the pathway to make siroheme remained to be identified. Here we identify and characterize a sirohydrochlorin-ferrochelatase from Paracoccus pantotrophus that catalyses the last step of siroheme synthesis. It is encoded by a gene annotated as cbiX that was previously assumed to be encoding a cobaltochelatase, acting on sirohydrochlorin. Expressing this chelatase from a plasmid restored the wild-type phenotype of an Escherichia coli mutant-strain lacking sirohydrochlorin-ferrochelatase activity, showing that this chelatase can act in the in vivo siroheme synthesis. A ΔcbiX mutant in P. denitrificans was unable to respire anaerobically on nitrate, proving the role of siroheme as a precursor to another cofactor. We report the 1.9 Å crystal structure of this ferrochelatase. In vivo analysis of single amino acid variants of this chelatase suggests that two histidines, His127 and His187, are essential for siroheme synthesis. This CbiX can generally be identified in α-proteobacteria as the terminal enzyme of siroheme biosynthesis.