Cofactor F430

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Cofactor F430
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
  • InChI=1S/C42H52N6O13.Ni/c1-40(16-30(43)50)22(5-9-33(54)55)27-15-42-41(2,17-31(51)48-42)23(6-10-34(56)57)26(47-42)13-24-20(11-35(58)59)19(4-8-32(52)53)39(45-24)37-28(49)7-3-18-21(12-36(60)61)25(46-38(18)37)14-29(40)44-27;/h13,18-23,25,27H,3-12,14-17H2,1-2H3,(H9,43,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61);/p-1/t18-,19-,20-,21-,22+,23+,25+,27-,40-,41-,42-;/m0./s1
    Key: QFGKGCZCUVIENT-SXMZNAGASA-M
  • CC12CC(=O)NC13CC4C(C(C(=N4)CC5C(C6CCC(=O)C(=C7C(C(C(=CC(=N3)C2CCC(=O)O)[N-]7)CC(=O)O)CCC(=O)O)C6=N5)CC(=O)O)(C)CC(=O)N)CCC(=O)O.[Ni]
Properties
C
42
H
51
N
6
NiO
13
Molar mass 906.58014
Appearance Yellow solid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

F430 is the

methyl coenzyme M reductase (MCR).[1][2]
MCR catalyzes the reaction EC 2.8.4.1 that releases methane in the final step of methanogenesis:

CH
3
–S–CoM
+ HS–CoBCH
4
+ CoB–S–S–CoM
Structure of coenzyme M (HS-CoM)
Structure of coenzyme B (HS-CoB)

It is found only in methanogenic Archaea[3] and anaerobic methanotrophic Archaea. It occurs in relatively high concentrations in archaea that are involved in reverse methanogenesis: these can contain up to 7% by weight of the nickel protein.[4]

Structure

The

macrocyclic ring system called a corphin.[8] In addition, it possesses two additional rings in comparison to the standard tetrapyrrole (rings A-D), having a γ-lactam ring E and a keto-containing carbocyclic ring F. It is the only natural tetrapyrrole containing nickel, an element rarely found in biological systems.[9]

Biosynthesis

uroporphyrinogen III
dihydrosirohydrochlorin
sirohydrochlorin

The biosynthesis builds from

biosynthesis of cobalamin, here giving nickel(II)-sirohydrochlorin.[11]

Nickel(II)-sirohydrochlorin a,c-diamide is converted to seco-F430. It is traditional to depict only one of four Ni-N bonds.

The ATP-dependent Ni-sirohydrochlorin a,c-diamide synthase (CfbE) then converts the a and c acetate side chains to acetamide in reactions EC 6.3.5.12, generating nickel(II)-sirohydrochlorin a,c-diamide. The sequence of the two amidations is random.[11] A two-component complex Ni-sirohydrochlorin a,c-diamide reductive cyclase (CfbCD) carries out a 6-electron and 7-proton reduction of the ring system in a reaction EC 6.3.3.7 generating the 15,173-seco-F430-173-acid (seco-F430) intermediate. Reduction involves ATP hydrolysis and electrons are relayed through two 4Fe-4S centres. In the final step, the keto-containing carbocyclic ring F is formed by an ATP-dependent enzyme Coenzyme F(430) synthetase (CfbB) in reaction EC 6.4.1.9, generating coenzyme F430.[11][12][13] This enzyme is a MurF-like ligase, as found in peptidoglycan biosynthesis.

References