Non-selective cation channel-2 family
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.
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.
References
- ^ a b 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.
- ^ 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. Vol. 66. pp. 289–295. doi:10.1007/978-3-0348-7327-7_23. ISBN 978-3-0348-7329-1. ISSN 1023-294X. PMID 7505659.
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