PDBsum entry 1pjs

Transferase/oxidoreductase/lyase

PDB id: 1pjs

Contents

Protein chains

443 a.a. *

Ligands

SAH ×2

NAD ×2

PGE ×2

PO4

Waters ×212

* Residue conservation analysis

PDB id:

1pjs

Name:

Transferase/oxidoreductase/lyase

Title:

The co-crystal structure of cysg, the multifunctional methyltransferase/dehydrogenase/ferrochelatase for siroheme synthesis, in complex with it NAD cofactor

Structure:

Siroheme synthase. Chain: a, b. Synonym: cysg. Engineered: yes. Other_details: residues 1-212 (cysgb) are a dehydrogenase/ferrochelatase, residues 213-457 (cysga) are a bismethyltransferase

Source:

Salmonella typhimurium. Organism_taxid: 602. Gene: cysg or stm3477. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PQS)

Resolution:

2.40Å R-factor: 0.239 R-free: 0.281

Authors:

M.E.Stroupe,H.K.Leech,D.S.Daniels,M.J.Warren,E.D.Getzoff

Key ref:

M.E.Stroupe et al. (2003). CysG structure reveals tetrapyrrole-binding features and novel regulation of siroheme biosynthesis. Nat Struct Biol, 10, 1064-1073. PubMed id: 14595395 DOI: 10.1038/nsb1007

Date:

03-Jun-03 Release date: 02-Dec-03

Protein chains

P25924  (CYSG_SALTY) -  Siroheme synthase from Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720)

Seq: 457 a.a.

Struc: 443 a.a.

Enzyme reactions

• Enzyme class 1: E.C.1.3.1.76 - precorrin-2 dehydrogenase.
• Pathway: Corrin and Siroheme Biosynthesis (part 2)
• Reaction: precorrin-2 + NAD⁺ = sirohydrochlorin + NADH + 2 H⁺

precorrin-2 (Bound ligand (Het Group name = NAD) corresponds exactly) + NAD(+) = sirohydrochlorin + NADH + 2 × H(+)

• Enzyme class 2: E.C.2.1.1.107 - uroporphyrinogen-III C-methyltransferase.

Pathway:

• Reaction: uroporphyrinogen III + 2 S-adenosyl-L-methionine = precorrin-2 + 2 S-adenosyl-L-homocysteine + H⁺

uroporphyrinogen III + 2 × S-adenosyl-L-methionine = precorrin-2 + 2 × S-adenosyl-L-homocysteine + 2 × H(+) (Bound ligand (Het Group name = SAH) corresponds exactly)

• Enzyme class 3: E.C.4.99.1.4 - sirohydrochlorin ferrochelatase.

Pathway:

• Reaction: siroheme + 2 H⁺ = sirohydrochlorin + Fe²⁺

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

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

reference

DOI no: 10.1038/nsb1007

Nat Struct Biol 10:1064-1073 (2003)

PubMed id: 14595395

CysG structure reveals tetrapyrrole-binding features and novel regulation of siroheme biosynthesis.

M.E.Stroupe, H.K.Leech, D.S.Daniels, M.J.Warren, E.D.Getzoff.

ABSTRACT

Sulfur metabolism depends on the iron-containing porphinoid siroheme. In Salmonella enterica, the S-adenosyl-L-methionine (SAM)-dependent bismethyltransferase, dehydrogenase and ferrochelatase, CysG, synthesizes siroheme from uroporphyrinogen III (uro'gen III). The reactions mediated by CysG encompass two branchpoint intermediates in tetrapyrrole biosynthesis, diverting flux first from protoporphyrin IX biosynthesis and then from cobalamin (vitamin B(12)) biosynthesis. We determined the first structure of this multifunctional siroheme synthase by X-ray crystallography. CysG is a homodimeric gene fusion product containing two structurally independent modules: a bismethyltransferase and a dual-function dehydrogenase-chelatase. The methyltransferase active site is a deep groove with a hydrophobic patch surrounded by hydrogen bond donors. This asymmetric arrangement of amino acids may be important in directing substrate binding. Notably, our structure shows that CysG is a phosphoprotein. From mutational analysis of the post-translationally modified serine, we suggest a conserved role for phosphorylation in inhibiting dehydrogenase activity and modulating metabolic flux between siroheme and cobalamin pathways.

Selected figure(s)

Figure 1.
Figure 1. Siroheme biosynthesis and its relationship to cobalamin (vitamin B[12]) and protoporphyrin IX-derived macrocycles (heme and chlorophyll).

Figure 5.
Figure 5. A stereo view of the methyltransferase active site from the native CysG structure, which sits deep within a cleft between the domains IA and IIA. (a) SAH (green) remains bound in the active site during purification and crystallization. Residues that bind SAH and that form the hydrophobic platform in the center of the active site are purple. Atoms are colored as in Figure 3. (b) The methyltransferase active site is an asymmetric slot with charged residues (blue) circling a hydrophobic patch (purple). (c) A model of uro'gen III in the CysGA active site. Uro'gen III is dark gray. This tetrapyrrole-binding model demonstrates the relationship among residues we know to be important for the methyltransferase reaction in the context of bound substrate. Same view as in b. The reactive pyrrole group is marked with an asterisk.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nat Struct Biol (2003, 10, 1064-1073) copyright 2003.

Figures were selected by an automated process.