Arsenite-antimonite transporter

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Arsenite-antimonite transporters are membrane transporters that pump arsenite or antimonite out of a cell. Antimonite is the salt of antimony (Sb(III)) and has been found to significantly impact the toxicity of arsenite. [1] The similar structure of As(III) and Sb(III) makes it plausible that certain transporters function in the efflux of both substrates. Arsenic efflux transporters exist in almost every organism and serve to remove this toxic compound from the cell. [2]

Contents

Subfamilies

As of early 2016, there are at least three known families of proteins known to participate in arsenite and antimonite efflux.

The membrane transporter ArsB can function as a secondary carrier or as a primary active transporter, in which case ArsA, an ATPase, must be superimposed onto ArsB. Arsenite and antimonite can also be pumped out of the cell by members of the ARC3 family, a member of the BART superfamily, which can participate in both secondary transport or primary active transport. Based on operon analyses, Arc3 homologues may similarly function either as secondary carriers or as primary active transporters. In the latter case ATP hydrolysis again energizes transport. [3]

See also

Related Research Articles

In cellular biology, active transport is the movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. Active transport requires cellular energy to achieve this movement. There are two types of active transport: primary active transport that uses adenosine triphosphate (ATP), and secondary active transport that uses an electrochemical gradient. An example of active transport in human physiology is the uptake of glucose in the intestines.

ATPase dephosphorylation enzyme

ATPases (EC 3.6.1.3, adenylpyrophosphatase, ATP monophosphatase, triphosphatase, SV40 T-antigen, adenosine 5'-triphosphatase, ATP hydrolase, complex V (mitochondrial electron transport), (Ca2+ + Mg2+)-ATPase, HCO3−-ATPase, adenosine triphosphatase) are a class of enzymes that catalyze the decomposition of ATP into ADP and a free phosphate ion or the inverse reaction. This dephosphorylation reaction releases energy, which the enzyme (in most cases) harnesses to drive other chemical reactions that would not otherwise occur. This process is widely used in all known forms of life.

A membrane transport protein is a membrane protein involved in the movement of ions, small molecules, and macromolecules, such as another protein, across a biological membrane. Transport proteins are integral transmembrane protein; that is they exist permanently within and span the membrane across which they transport substances. The proteins may assist in the movement of substances by facilitated diffusion or active transport. The two main types of proteins involved in such transport are broadly categorized as either channels or carriers. The solute carriers and atypical SLCs are secondary active or facilitative transporters in humans. Collectively membrane transporters and channels are transportome. Transportomes govern cellular influx and efflux of not only ions and nutrients but drugs as well.

ATP-binding cassette transporter group of transmembrane transport proteins

The ATP-binding cassette transporters are a transport system superfamily that is one of the largest and possibly one of the oldest gene families. It is represented in all extant phyla, from prokaryotes to humans.

The Transporter Classification Database is an International Union of Biochemistry and Molecular Biology (IUBMB)-approved classification system for membrane transport proteins, including ion channels.

In biology, an ion transporter is a transmembrane protein that moves ions across a biological membrane against their concentration gradient through active transport. These primary transporters are enzymes that convert energy from various sources—including adenosine triphosphate (ATP), sunlight, and other redox reactions—to potential energy stored in an electrochemical gradient. This potential energy is then used by secondary transporters, including ion carriers and ion channels, to drive vital cellular processes, such as ATP synthesis.

Method of glucose uptake differs throughout tissues depending on two factors; the metabolic needs of the tissue and availability of glucose. The two ways in which glucose uptake can take place are facilitated diffusion and secondary active transport. Active transport is the movement of ions or molecules going against the concentration gradient.

Efflux (microbiology)

All microorganisms, with a few exceptions, have highly conserved DNA sequences in their genome that are transcribed and translated to efflux pumps. Efflux pumps are capable of moving a variety of different toxic compounds out of cells, such as antibiotics, heavy metals, organic pollutants, plant-produced compounds, quorum sensing signals, bacterial metabolites and neurotransmitters via active efflux, which is vital part for xenobiotic metabolism. This active efflux mechanism is responsible for various types of resistance to bacterial pathogens within bacterial species - the most concerning being antibiotic resistance because microorganisms can have adapted efflux pumps to divert toxins out of the cytoplasm and into extracellular media.

Translocase is a general term for a protein that assists in moving another molecule, usually across a cell membrane. These enzymes catalyze the movement of ions or molecules across membranes or their separation within membranes. The reaction is designated as a transfer from “side 1” to “side 2” because the designations “in” and “out”, which had previously been used, can be ambiguous. Translocases are the most common secretion system in Gram positive bacteria.

In enzymology, an arsenite-transporting ATPase (EC 3.6.3.16) is an enzyme that catalyzes the chemical reaction

P-type ATPase group of membrane proteins that catalyze cation uptake and/or efflux driven by ATP hydrolysis

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In enzymology, a polyphosphate kinase, or polyphosphate polymerase, is an enzyme that catalyzes the formation of polyphosphate from ATP, with chain lengths of up to a thousand or more orthophosphate moieties.

ATPase ASNA1 protein-coding gene in the species Homo sapiens

ATPase ASNA1 also known as arsenical pump-driving ATPase and arsenite-stimulated ATPase is an enzyme that in humans is encoded by the ASNA1 gene.

The ATPase assay is a membrane assay that indirectly measures the activity of efflux transporters. ATP Binding Cassette or efflux transporters mediate the transport of substrates across cell membranes against a concentration gradient. ATP cleavage is tightly linked to substrate translocation, as the energy for the substrate translocation is derived from ATP hydrolysis. ATP hydrolysis yields inorganic phosphate (Pi), which can be measured by a simple colorimetric reaction. The amount of Pi liberated is directly proportional to the activity of the transporter.

Ars operon

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.

The multidrug/oligosaccharidyl-lipid/polysaccharide (MOP) flippase superfamily is a group of integral membrane protein families. The MOP flippase superfamily includes twelve distantly related families, six for which functional data are available:

  1. One ubiquitous family (MATE) specific for drugs - (TC# 2.A.66.1) The Multi Antimicrobial Extrusion (MATE) Family
  2. One (PST) specific for polysaccharides and/or their lipid-linked precursors in prokaryotes - (TC# 2.A.66.2) The Polysaccharide Transport (PST) Family
  3. One (OLF) specific for lipid-linked oligosaccharide precursors of glycoproteins in eukaryotes - (TC# 2.A.66.3) The Oligosaccharidyl-lipid Flippase (OLF) Family
  4. One (MVF) lipid-peptidoglycan precursor flippase involved in cell wall biosynthesis - (TC# 2.A.66.4) The Mouse Virulence Factor (MVF) Family
  5. One (AgnG) which includes a single functionally characterized member that extrudes the antibiotic, Agrocin 84 - (TC# 2.A.66.5) The Agrocin 84 Antibiotic Exporter (AgnG) Family
  6. And finally, one (Ank) that shuttles inorganic pyrophosphate (PPi) - (TC# 2.A.66.9) The Progressive Ankylosis (Ank) Family

The ion transporter (IT) superfamily is a superfamily of secondary carriers that transport charged substrates.

The Bile/Arsenite/Riboflavin Transporter (BART) superfamily is a superfamily of ubiquitous transport proteins. As of early 2016, the superfamily contains seven established families. Functional data for members of all of these families are available. The seven families are in the Transporter Classification Database with the following TC numbers, names and abbreviations include:

Arsenite resistance (Ars) efflux pumps of bacteria may consist of two proteins, ArsB and ArsA, or of one protein. ArsA proteins have two ATP binding domains and probably arose by a tandem gene duplication event. ArsB proteins all possess twelve transmembrane spanners and may also have arisen by a tandem gene duplication event. Structurally, the Ars pumps resemble ABC-type efflux pumps, but there is no significant sequence similarity between the Ars and ABC pumps. When only ArsB is present, the system operates by a pmf-dependent mechanism, and consequently belongs in TC subclass 2.A. When ArsA is also present, ATP hydrolysis drives efflux, and consequently the system belongs in TC subclass 3.A. ArsB therefore appears twice in the TC system but ArsA appears only once. These pumps actively expel both arsenite and antimonite.

The arsenical resistance-3 (ACR3) family is a member of the BART superfamily. Based on operon analyses, ARC3 homologues may function either as secondary carriers or as primary active transporters, similarly to the ArsB and ArsAB families. In the latter case ATP hydrolysis again energizes transport. ARC3 homologues transport the same anions as ArsA/AB homologues, though ArsB homologues are members of the IT Superfamily and homologues of the ARC3 family are within the BART Superfamily suggesting they may not be evolutionarily related.

References

  1. ↑ Hasgekar, N.; Beck, J. P.; Dunkelberg, H.; Hirsch-Ernst, K. I.; Gebel, T. W. (2006-01-01). "Influence of antimonite, selenite, and mercury on the toxicity of arsenite in primary rat hepatocytes". Biological Trace Element Research. 111 (1–3): 167–183. doi:10.1385/BTER:111:1:167. ISSN   0163-4984. PMID   16943604. S2CID   23224806.
  2. ↑ Yang, Hung-Chi; Fu, Hsueh-Liang; Lin, Yung-Feng; Rosen, Barry P. (2012-01-01). "Pathways of arsenic uptake and efflux". Current Topics in Membranes. 69: 325–358. doi:10.1016/B978-0-12-394390-3.00012-4. ISBN   9780123943903. ISSN   1063-5823. PMC   4578627 . PMID   23046656.
  3. ↑ "TCDB » SEARCH". www.tcdb.org. Retrieved 2016-03-13.


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