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MetaCyc Polypeptide: corrinoid/iron-sulfur protein α subunit

Gene: acsD Accession Number: G-3402 (MetaCyc)

Synonyms: corrinoid/Fe-S protein, α subunit, E[Co]-α subunit

Species: Moorella thermoacetica

Component of: AcsCD corrinoid/iron-sulfur protein complex (extended summary available)

Alternative forms of AcsCD corrinoid/iron-sulfur protein complex: corrinoid/iron-sulfur protein, methylated (extended summary available)

Gene Citations: [Lu93]

Molecular Weight of Polypeptide: 33.0 kD (experimental) [Ragsdale87 ]

Unification Links: DIP:DIP-59670N , ModBase:Q07341 , Protein Model Portal:Q07341 , SMR:Q07341 , Swiss-Model:Q07341 , UniProt:Q07341

Relationship Links: Entrez-Nucleotide:PART-OF:L07100 , InterPro:IN-FAMILY:IPR004486 , InterPro:IN-FAMILY:IPR011005 , InterPro:IN-FAMILY:IPR016041 , PDB:Structure:4DJD , PDB:Structure:4DJE , PDB:Structure:4DJF , Pfam:IN-FAMILY:PF03599

Reactions known to produce the compound:

methanogenesis from acetate :
a [methyl-Co(III) corrinoid Fe-S protein] + tetrahydrosarcinapterin → a [Co(I) corrinoid Fe-S protein] + 5-methyl-tetrahydrosarcinapterin

Reactions known to both consume and produce the compound:

methanogenesis from acetate :
acetyl-CoA + a [Co(I) corrinoid Fe-S protein] ↔ carbon monoxide + a [methyl-Co(III) corrinoid Fe-S protein] + coenzyme A

reductive acetyl coenzyme A pathway :
acetyl-CoA + a [Co(I) corrinoid Fe-S protein] ↔ carbon monoxide + a [methyl-Co(III) corrinoid Fe-S protein] + coenzyme A
a tetrahydrofolate + a [methyl-Co(III) corrinoid Fe-S protein] ↔ an N5-methyl-tetrahydrofolate + a [Co(I) corrinoid Fe-S protein]

Gene-Reaction Schematic: ?

Gene Class: UNCLASSIFIED


Subunit of: AcsCD corrinoid/iron-sulfur protein complex

Synonyms: corrinoid/Fe-S protein, C/Fe-SP, E[Co]

Species: Moorella thermoacetica

Subunit composition of AcsCD corrinoid/iron-sulfur protein complex = [AcsD][AcsC]
         corrinoid/iron-sulfur protein α subunit = AcsD
         corrinoid/iron-sulfur protein β subunit = AcsC

Summary:
The AcsCD corrinoid/iron-sulfur protein complex (C/Fe-SP) from Moorella thermoacetica acts as a methyl group carrier in the reductive acetyl coenzyme A pathway of CO and CO2 fixation. It is a dimer, consisting of a small (-33 kDa) and a large (-55 kDa) subunits, and contains 1 mol of cobalt in a corrinoid cofactor and 1 mol of [4Fe-4S] cluster per mol of an αβ dimer. The corrinoid cofactor was shown to be 5-methoxybenzimidazolylcobamide [Ljungdahl65]. Even though the cobamide binding sites are located in the small subunit, both subunits are required for formation of a stable cobamide-binding protein [Lu93].

Prior to methylation the coblat must be in the highly reduced (I) state. During methylation the cobalt is oxidized to the (III) state, and is restored to the (I) state during demethylation. About once in 2000 reaction cycles the cobalt atom ends up in the (II) state, which is inactive. The inactive form can be reactivated by reduction of the cobalt to the (I) form. The [4Fe-4S] is involved in the reductive activation, and is able to transfer electrons from several sources, including reduced ferredoxins [Menon98].

The protein was first purified by Hu et al (1984). The genes encoding both subunits are located within a gene cluster that includes other genes required for CO2 fixation by anaerobic bacteria. The genes were cloned by [Roberts89] and eventually sequenced by [Lu93], who also expressed it in Escherichia coli.

Citations: [Diekert94, Ljungdahl86, Ragsdale87]

Molecular Weight: 89 kD (experimental) [Hu84]

Credits:
Revised 12-Dec-2011 by Caspi R , SRI International


Enzymatic reaction of: corrinoid/iron-sulfur protein

carbon tetrachloride + a reduced electron acceptor <=> trichloromethyl radical + chloride + an oxidized electron acceptor + 2 H+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is favored in the direction shown.

In Pathways: carbon tetrachloride degradation II

Summary:
This reaction is a non-specific, cometabolic reaction, in which the corrinoid protein catalyzes the reductive dechlorination of carbon tetrachloride to chloroform [Egli88]. The first part of the reaction is the generation of a radical [Krone91a]. This radical may be protonated to form chloroform, or alternatively it could eliminate a chloride and become a dichlorocarbene [Krone91a].


Enzymatic reaction of: chloroform dehalogenase (AcsCD corrinoid/iron-sulfur protein complex)

chloroform + H+ <=> dichloromethane + chloride

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is favored in the direction shown.

In Pathways: carbon tetrachloride degradation I

Summary:
This reaction is a non-specific, cometabolic reaction, in which the corrinoid protein catalyzes the reductive dechlorination of chloroform to dichloromethane [Egli88].


Enzymatic reaction of: carbon tetrachloride dehalogenase (AcsCD corrinoid/iron-sulfur protein complex)

carbon tetrachloride + H+ <=> chloroform + chloride

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is favored in the direction shown.

In Pathways: carbon tetrachloride degradation I

Summary:
This reaction is a non-specific, cometabolic reaction, in which the corrinoid protein catalyzes the reductive dechlorination of carbon tetrachloride to chloroform [Egli88].


References

Diekert94: Diekert G, Wohlfarth G (1994). "Metabolism of homocetogens." Antonie Van Leeuwenhoek 1994;66(1-3);209-21. PMID: 7747932

Egli88: Egli C, Tschan T, Scholtz R, Cook AM, Leisinger T (1988). "Transformation of tetrachloromethane to dichloromethane and carbon dioxide by Acetobacterium woodii." Appl Environ Microbiol 1988;54(11);2819-24. PMID: 3145712

Hu84: Hu SI, Pezacka E, Wood HG (1984). "Acetate synthesis from carbon monoxide by Clostridium thermoaceticum. Purification of the corrinoid protein." J Biol Chem 259(14);8892-7. PMID: 6746629

Krone91a: Krone UE, Thauer RK, Hogenkamp HP, Steinbach K (1991). "Reductive formation of carbon monoxide from CCl4 and FREONs 11, 12, and 13 catalyzed by corrinoids." Biochemistry 30(10);2713-9. PMID: 2001359

Ljungdahl65: Ljungdahl L, Irion E, Wood HG (1965). "Total synthesis of acetate from CO2. I. Co-methylcobyric acid and CO-(methyl)-5-methoxybenzimidazolylcobamide as intermediates with Clostridium thermoaceticum." Biochemistry 4(12);2771-80. PMID: 5880685

Ljungdahl86: Ljungdahl LG (1986). "The autotrophic pathway of acetate synthesis in acetogenic bacteria." Annu Rev Microbiol 1986;40;415-50. PMID: 3096193

Lu93: Lu WP, Schiau I, Cunningham JR, Ragsdale SW (1993). "Sequence and expression of the gene encoding the corrinoid/iron-sulfur protein from Clostridium thermoaceticum and reconstitution of the recombinant protein to full activity." J Biol Chem 268(8);5605-14. PMID: 8449924

Menon98: Menon S, Ragsdale SW (1998). "Role of the [4Fe-4S] cluster in reductive activation of the cobalt center of the corrinoid iron-sulfur protein from Clostridium thermoaceticum during acetate biosynthesis." Biochemistry 37(16);5689-98. PMID: 9548955

Ragsdale87: Ragsdale SW, Lindahl PA, Munck E (1987). "Mossbauer, EPR, and optical studies of the corrinoid/iron-sulfur protein involved in the synthesis of acetyl coenzyme A by Clostridium thermoaceticum." J Biol Chem 1987;262(29);14289-97. PMID: 2821001

Roberts89: Roberts DL, James-Hagstrom JE, Garvin DK, Gorst CM, Runquist JA, Baur JR, Haase FC, Ragsdale SW (1989). "Cloning and expression of the gene cluster encoding key proteins involved in acetyl-CoA synthesis in Clostridium thermoaceticum: CO dehydrogenase, the corrinoid/Fe-S protein, and methyltransferase." Proc Natl Acad Sci U S A 86(1);32-6. PMID: 2911576


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Mon Nov 24, 2014, BIOCYC14A.