Non-selective cation channel-2 family

Last updated

Members of the Non-Selective Cation Channel-2 (NSCC2) Family (TC#1.A.15) have been sequenced from various yeast, fungal and animals species including Saccharomyces cerevisiae , Drosophila melanogaster and Homo sapiens . [1] These proteins are the Sec62 proteins, believed to be associated with the Sec61 and Sec63 constituents of the general protein secretory systems of yeast microsomes. They are also the non-selective (NS) cation channels of the mammalian cytoplasmic membrane.

Contents

Function

NSCC2 channels are believed to provide entry pathways in response to growth factors. [2] The yeast Sec62 protein has been shown to be essential for cell growth. The mammalian NS channel proteins have been implicated in platelet derived growth factor (PDGF)-dependent single channel current in fibroblasts. These channels are essentially closed in serum deprived tissue-culture cells and are specifically opened by exposure to PDGF.

The channels are reported to exhibit equal selectivity for Na+ , K+ and Cs+ with low permeability to Ca2+ , and no permeability to anions. Channel open probability is voltage- and cytoplasmic Ca2+-independent.

Transport reaction

The generalized transport reaction catalyzed by members of the NSCC2 family is:

Cation (out) ⇌ cation (in)

Structure and location

Sequenced NSCC2 family proteins are 283-402 amino acyl residues in length and exhibit two putative transmembrane α-helical segments (TMSs). The S. cerevisiae protein, of 283 amino acyl residues, has cytoplasmic N- and C-termini with two putative TMSs at positions 159-178 and 193-213. The C-terminal 25 residues are rich in arginine and lysine. [1] These proteins have been reported to be present in both endoplasmic reticular and cytoplasmic membranes.

Related Research Articles

Calcium release-activated channels (CRAC) are specialized plasma membrane Ca2+ ion channels. When calcium ions (Ca2+) are depleted from the endoplasmic reticulum (a major store of Ca2+) of mammalian cells, the CRAC channel is activated to slowly replenish the level of calcium in the endoplasmic reticulum. The Ca2+ Release-activated Ca2+ (CRAC) Channel (CRAC-C) Family (TC# 1.A.52) is a member of the Cation Diffusion Facilitator (CDF) Superfamily. These proteins typically have between 4 and 6 transmembrane α-helical spanners (TMSs). The 4 TMS CRAC channels arose by loss of 2TMSs from 6TMS CDF carriers, an example of 'reverse' evolution'.

<span class="mw-page-title-main">Chloride channel</span> Class of transport proteins

Chloride channels are a superfamily of poorly understood ion channels specific for chloride. These channels may conduct many different ions, but are named for chloride because its concentration in vivo is much higher than other anions. Several families of voltage-gated channels and ligand-gated channels have been characterized in humans.

<span class="mw-page-title-main">Major intrinsic proteins</span>

Major intrinsic proteins comprise a large superfamily of transmembrane protein channels that are grouped together on the basis of homology. The MIP superfamily includes three subfamilies: aquaporins, aquaglyceroporins and S-aquaporins.

  1. The aquaporins (AQPs) are water selective.
  2. The aquaglyceroporins are permeable to water, but also to other small uncharged molecules such as glycerol.
  3. The third subfamily, with little conserved amino acid sequences around the NPA boxes, include 'superaquaporins' (S-aquaporins).

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.

The Nucleobase:Cation Symporter-1 (NCS1) Family (TC# 2.A.39) consists of over 1000 currently sequenced proteins derived from Gram-negative and Gram-positive bacteria, archaea, fungi and plants. These proteins function as transporters for nucleobases including purines and pyrimidines. Members of this family possess twelve transmembrane α-helical spanners (TMSs). At least some of them have been shown to function in uptake by substrate:H+ symport mechanism.

Small conductance mechanosensitive ion channels (MscS) provide protection against hypo-osmotic shock in bacteria, responding both to stretching of the cell membrane and to membrane depolarization. In eukaryotes, they fulfill a multitude of important functions in addition to osmoregulation. They are present in the membranes of organisms from the three domains of life: bacteria, archaea, fungi and plants.

The lysosomal cystine transporter (LCT) family is part of the TOG Superfamily and includes secondary transport proteins that are derived from animals, plants, fungi and other eukaryotes. They exhibit 7 putative transmembrane α-helical spanners (TMSs) and vary in size between about 200 and 500 amino acyl residues, although most have between 300 and 400 residues.

The cation-chloride cotransporter (CCC) family is part of the APC superfamily of secondary carriers. Members of the CCC family are found in animals, plants, fungi and bacteria. Most characterized CCC family proteins are from higher eukaryotes, but one has been partially characterized from Nicotiana tabacum, and homologous ORFs have been sequenced from Caenorhabditis elegans (worm), Saccharomyces cerevisiae (yeast) and Synechococcus sp.. The latter proteins are of unknown function. These proteins show sequence similarity to members of the APC family. CCC family proteins are usually large, and possess 12 putative transmembrane spanners (TMSs) flanked by large N-terminal and C-terminal hydrophilic domains.

The potassium (K+) uptake permease (KUP) family (TC# 2.A.72) is a member of the APC superfamily of secondary carriers. Proteins of the KUP/HAK/KT family include the KUP (TrkD) protein of E. coli and homologues in both Gram-positive and Gram-negative bacteria. High affinity (20 μM) K+ uptake systems (Hak1, TC# 2.A.72.2.1) of the yeast Debaryomyces occidentalis as well as the fungus, Neurospora crassa, and several homologues in plants have been characterized. Arabidopsis thaliana and other plants possess multiple KUP family paralogues. While many plant proteins cluster tightly together, the Hak1 proteins from yeast as well as the two Gram-positive and Gram-negative bacterial proteins are distantly related on the phylogenetic tree for the KUP family. All currently classified members of the KUP family can be found in the Transporter Classification Database.

The Ca2+:cation antiporter (CaCA) family (TC# 2.A.19) is a member of the cation diffusion facilitator (CDF) superfamily. This family should not be confused with the Ca2+:H+ Antiporter-2 (CaCA2) Family (TC# 2.A.106) which belongs to the Lysine Exporter (LysE) Superfamily. Proteins of the CaCA family are found ubiquitously, having been identified in animals, plants, yeast, archaea and divergent bacteria. Members of this family facilitate the antiport of calcium ion with another cation.

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 iron/lead transporter (ILT) family is a family of transmembrane proteins within the lysine exporter (LysE) superfamily. The ILT family includes two subfamilies, the iron-transporting (OFeT) family and the lead-transporting (PbrT) family. A representative list of the proteins belonging to these subfamilies of the ILT family can be found in the Transporter Classification Database.

Divalent anion:Na+ symporters were found in bacteria, archaea, plant chloroplasts and animals.

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.

<span class="mw-page-title-main">Monovalent cation:proton antiporter-1</span> Family of proteins

The Monovalent Cation:Proton Antiporter-1 (CPA1) Family (TC# 2.A.36) is a large family of proteins derived from Gram-positive and Gram-negative bacteria, blue-green bacteria, archaea, yeast, plants and animals. The CPA1 family belongs to the VIC superfamily. Transporters from eukaryotes have been functionally characterized to catalyze Na+:H+ exchange. Their primary physiological functions are thought to be in (1) cytoplasmic pH regulation, extruding the H+ generated during metabolism, and (2) salt tolerance (in plants), due to Na+ uptake into vacuoles. Bacterial homologues have also been found to facilitate Na+:H+ antiport, but some also catalyze Li+:H+ antiport or Ca2+:H+ antiport under certain conditions.

The inorganic phosphate transporter (PiT) family is a group of carrier proteins derived from Gram-negative and Gram-positive bacteria, archaea, and eukaryotes.

The ryanodine-inositol 1,4,5-triphosphate receptor Ca2+ channel (RIR-CaC) family includes Ryanodine receptors and Inositol trisphosphate receptors. Members of this family are large proteins, some exceeding 5000 amino acyl residues in length. This family belongs to the Voltage-gated ion channel (VIC) superfamily. Ry receptors occur primarily in muscle cell sarcoplasmic reticular (SR) membranes, and IP3 receptors occur primarily in brain cell endoplasmic reticular (ER) membranes where they effect release of Ca2+ into the cytoplasm upon activation (opening) of the channel. They are redox sensors, possibly providing a partial explanation for how they control cytoplasmic Ca2+. Ry receptors have been identified in heart mitochondria where they provide the main pathway for Ca2+ entry. Sun et al. (2011) have demonstrated oxygen-coupled redox regulation of the skeletal muscle ryanodine receptor-Ca2+ release channel (RyR1;TC# 1.A.3.1.2) by NADPH oxidase 4.

The Polycystin Cation Channel (PCC) Family consists of several transporters ranging in size from 500 to over 4000 amino acyl residues (aas) in length and exhibiting between 5 and 18 transmembrane segments (TMSs). This family is a constituent of the Voltage-Gated Ion Channel (VIC) Superfamily. These transporters generally catalyze the export of cations. A representative list of proteins belonging to the PCC family can be found in the Transporter Classification Database.

The transient receptor potential Ca2+ channel (TRP-CC) family (TC# 1.A.4) is a member of the voltage-gated ion channel (VIC) superfamily and consists of cation channels conserved from worms to humans. The TRP-CC family also consists of seven subfamilies (TRPC, TRPV, TRPM, TRPN, TRPA, TRPP, and TRPML) based on their amino acid sequence homology:

  1. the canonical or classic TRPs,
  2. the vanilloid receptor TRPs,
  3. the melastatin or long TRPs,
  4. ankyrin (whose only member is the transmembrane protein 1 [TRPA1])
  5. TRPN after the nonmechanoreceptor potential C (nonpC), and the more distant cousins,
  6. the polycystins
  7. and mucolipins.

The testis-enhanced gene transcript (TEGT) family includes the testis-enhanced gene transcript proteins of mammals, which are expressed at high levels in the testis, the putative glutamate/aspartate binding proteins of plants and animals, the YccA protein of Escherichia coli and the YetJ protein of Bacillus subtilis. These proteins are about 200-250 residues in length and exhibit 7 TMSs.

References

  1. 1 2 Bihler, H.; Slayman, C. L.; Bertl, A. (1998-07-31). "NSC1: a novel high-current inward rectifier for cations in the plasma membrane of Saccharomyces cerevisiae". FEBS Letters. 432 (1–2): 59–64. doi: 10.1016/s0014-5793(98)00832-1 . ISSN   0014-5793. PMID   9710251. S2CID   23925844.
  2. ↑ Gargus, J. J.; Frace, A. M.; Jung, F. (1993-01-01). "The Role of a PDGF-Activated Nonselective Cation Channel in the Proliferative Response". Nonselective Cation Channels. pp. 289–295. doi:10.1007/978-3-0348-7327-7_23. ISBN   978-3-0348-7329-1. ISSN   1023-294X. PMID   7505659.{{cite book}}: |journal= ignored (help)

As of this edit, this article uses content from "1.A.15 The Non-selective Cation Channel-2 (NSCC2) Family" , which is licensed in a way that permits reuse under the Creative Commons Attribution-ShareAlike 3.0 Unported License, but not under the GFDL. All relevant terms must be followed.

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.