Summary: ArsC family
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Ars operon Edit Wikipedia article
yffb (pa3664) protein
In molecular biology, the ars operon is an operon found in several bacterial taxon. It is required for the detoxification of arsenate, arsenite, and antimonite. This system transports arsenite and antimonite out of the cell. The pump is composed of two polypeptides, the products of the arsA and arsB genes. This two-subunit enzyme produces resistance to arsenite and antimonite. Arsenate, however, must first be reduced to arsenite before it is extruded. A third gene, arsC, expands the substrate specificity to allow for arsenate pumping and resistance. ArsC is an approximately 150-residue arsenate reductase that uses reduced glutathione (GSH) to convert arsenate to arsenite with a redox active cysteine residue in the active site. ArsC forms an active quaternary complex with GSH, arsenate, and glutaredoxin 1 (Grx1). The three ligands must be present simultaneously for reduction to occur.
ArsA and ArsB
ArsA and ArsB form an anion-translocating ATPase. The ArsB protein is distinguished by its overall hydrophobic character, in keeping with its role as a membrane-associated channel. Sequence analysis reveals the presence of 13 putative transmembrane (TM) regions.
The arsC protein structure has been solved. It belongs to the thioredoxin superfamily fold which is defined by a beta-sheet core surrounded by alpha-helices. The active cysteine residue of ArsC is located in the loop between the first beta-strand and the first helix, which is also conserved in the Spx protein and its homologues.
ArsD and ArsR
ArsD is a trans-acting repressor of the arsRDABC operon that confers resistance to arsenicals and antimonials in Escherichia coli. It possesses two-pairs of vicinal cysteine residues, Cys(12)-Cys(13) and Cys(112)-Cys(113), that potentially form separate binding sites for the metalloids that trigger dissociation of ArsD from the operon. However, as a homodimer it has four vicinal cysteine pairs. The ArsD family consists of several bacterial arsenical resistance operon trans-acting repressor ArsD proteins.
ArsR is a trans-acting regulatory protein. It acts as a repressor on the arsRDABC operon when no arsenic is present in the cell. When arsenic is present in the cell ArsR will lose affinity for the operator and RNA polymerase can transcribe the arsDCAB genes. ArsD and ArsR work together to regulate the ars operon.
arsenic chaperone, ArsD, encoded by the arsRDABC operon of Escherichia coli. ArsD transfers trivalent metalloids to ArsA, the catalytic subunit of an As(III)/Sb(III) efflux pump. Interaction with ArsD increases the affinity of ArsA for arsenite, thus increasing its ATPase activity at lower concentrations of arsenite and enhancing the rate of arsenite extrusion. 
- Carlin A, Shi W, Dey S, Rosen BP (February 1995). "The ars operon of Escherichia coli confers arsenical and antimonial resistance". J. Bacteriol. 177 (4): 981â€“6. PMC 176692. PMID 7860609.
- Liu J, Rosen BP (August 1997). "Ligand interactions of the ArsC arsenate reductase". J. Biol. Chem. 272 (34): 21084â€“9. doi:10.1074/jbc.272.34.21084. PMID 9261111.
- Rosen BP (1990). "The plasmid-encoded arsenical resistance pump: an anion-translocating ATPase.". Res Microbiol 141 (3): 336â€“41. doi:10.1016/0923-2508(90)90008-e. PMID 1704144.
- Martin P, DeMel S, Shi J, Gladysheva T, Gatti DL, Rosen BP, Edwards BF (November 2001). "Insights into the structure, solvation, and mechanism of ArsC arsenate reductase, a novel arsenic detoxification enzyme". Structure 9 (11): 1071â€“81. doi:10.1016/S0969-2126(01)00672-4. PMID 11709171.
- Zuber P (April 2004). "Spx-RNA polymerase interaction and global transcriptional control during oxidative stress". J. Bacteriol. 186 (7): 1911â€“8. doi:10.1128/jb.186.7.1911-1918.2004. PMC 374421. PMID 15028674.
- Li S, Rosen BP, Borges-Walmsley MI, Walmsley AR (July 2002). "Evidence for cooperativity between the four binding sites of dimeric ArsD, an As(III)-responsive transcriptional regulator". J. Biol. Chem. 277 (29): 25992â€“6002. doi:10.1074/jbc.M201619200. PMID 11980902.
ArsC family Provide feedback
This family is related to glutaredoxins PF00462.
Internal database links
|SCOOP:||SH3BGR Viral_NABP DUF836 DUF1223 MalM DUF1687 SSXRD DUF2052 Ish1 TilS_C GST_N_3 DUF4902 DUF5039 Spike_NTD|
|Similarity to PfamA using HHSearch:||Glutaredoxin|
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR006660
Several bacterial taxon have a chromosomal resistance system, encoded by the ars operon, for the detoxification of arsenate, arsenite, and antimonite [PUBMED:7860609]. This system transports arsenite and antimonite out of the cell. The pump is composed of two polypeptides, the products of the arsA and arsB genes. This two-subunit enzyme produces resistance to arsenite and antimonite. Arsenate, however, must first be reduced to arsenite before it is extruded. A third gene, arsC, expands the substrate specificity to allow for arsenate pumping and resistance. ArsC is an approximately 150-residue arsenate reductase that uses reduced glutathione (GSH) to convert arsenate to arsenite with a redox active cysteine residue in the active site. ArsC forms an active quaternary complex with GSH, arsenate, and glutaredoxin 1 (Grx1). The three ligands must be present simultaneously for reduction to occur [PUBMED:9261111].
The arsC family also comprises the Spx proteins which are GRAM-positive bacterial transcription factors that regulate the transcription of multiple genes in response to disulphide stress [PUBMED:15028674].
The arsC protein structure has been solved [PUBMED:11709171]. It belongs to the thioredoxin superfamily fold which is defined by a beta-sheet core surrounded by alpha-helices. The active cysteine residue of ArsC is located in the loop between the first beta-strand and the first helix, which is also conserved in the Spx protein and its homologues.
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This clan contains families related to the thioredoxin family. Thioredoxins are small enzymes that are involved in redox reactions via the reversible oxidation of an active centre disulfide bond. The thioredoxin fold consists of a 3 layer alpha/beta/alpha sandwich and a central beta sheet.
The clan contains the following 52 members:2Fe-2S_thioredx AhpC-TSA AhpC-TSA_2 Aminopep ArsC ArsD Calsequestrin DIM1 DSBA DUF1223 DUF1525 DUF1687 DUF2703 DUF2847 DUF4174 DUF836 DUF899 DUF953 ERp29_N Glutaredoxin GSHPx GST_N GST_N_2 GST_N_3 HyaE KaiB L51_S25_CI-B8 Metallopep MRP-S23 MRP-S25 Peptidase_M76 Phosducin Redoxin SCO1-SenC SelP_N Sep15_SelM SH3BGR T4_deiodinase Thioredox_DsbH Thioredoxin Thioredoxin_2 Thioredoxin_3 Thioredoxin_4 Thioredoxin_5 Thioredoxin_6 Thioredoxin_7 Thioredoxin_8 Thioredoxin_9 Tom37 TraF YtfJ_HI0045 Zincin_1
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Curation and family details
|Number in seed:||35|
|Number in full:||34904|
|Average length of the domain:||108.60 aa|
|Average identity of full alignment:||29 %|
|Average coverage of the sequence by the domain:||87.21 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 80369284 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||11|
|Download:||download the raw HMM for this family|
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There are 2 interactions for this family. More...
We determine these interactions using iPfam, which considers the interactions between residues in three-dimensional protein structures and maps those interactions back to Pfam families. You can find more information about the iPfam algorithm in the journal article that accompanies the website.
For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the ArsC domain has been found. There are 26 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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