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首页> 外文期刊>Canadian Journal of Physiology and Pharmacology >Functional characterization of the transmembrane segment VII of the NHE1 isoform of the Na+/H+ exchanger.
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Functional characterization of the transmembrane segment VII of the NHE1 isoform of the Na+/H+ exchanger.

机译：Na + / H +交换剂的NHE1同工型的跨膜片段VII的功能表征。

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摘要

The Na+/H+ exchanger isoform 1 is an integral membrane protein that regulates intracellular pH. It extrudes 1 intracellular H+ in exchange for 1 extracellular Na+. It has 2 large domains, an N-terminal membrane domain of 12 transmembrane segments and an intracellular C-terminal regulatory domain. We characterized the cysteine accessibility of amino acids of the critical transmembrane segment TM VII. Residues Leu 255, Leu 258, Glu 262, Leu 265, Asn 266, Asp 267, Val 269, Val 272, and Leu 273 were all mutated to cysteine residues in the cysteineless NHE1 isoform. Mutation of amino acids E262, N266, and D267 caused severe defects in activity and targeting of the intact full length protein. The balance of the active mutants were examined for sensitivity to the sulfhydryl reactive reagents, positively charged MTSET ((2- (trimethylammonium)ethyl)methanethiosulfonate) and negatively charged MTSES ((2-sulfonatoethyl)methanethiosulfonate). Leu 255 and Leu 258 were sensitive to MTSET but not to MTSES. The results suggest that these amino acids are pore-lining residues. We present a model of TM VII that shows that residues Leu 255, Leu 258, Glu 262, Asn 266, and Asp 267 lie near the same face of TM VII, lining the ion transduction pore.
机译：Na + / H +交换异构体1是调节细胞内pH的完整膜蛋白。它挤出1个细胞内H +交换1个细胞外Na +。它具有2个大域，一个12跨膜段的N末端膜域和一个细胞内C末端调节域。我们表征了关键跨膜片段TM VII的氨基酸的半胱氨酸可及性。残基Leu 255，Leu 258，Glu 262，Leu 265，Asn 266，Asp 267，Val 269，Val 272和Leu 273均突变为无半胱氨酸NHE1亚型中的半胱氨酸残基。氨基酸E262，N266和D267的突变导致活性和完整全长蛋白质靶向的严重缺陷。检查了活性突变体的其余部分对巯基反应性试剂，带正电的MTSET（（2-（三甲铵）乙基）甲硫代磺酸盐）和带负电的MTSES（（2-磺酰氨基乙基）甲硫代磺酸盐）的敏感性。 Leu 255和Leu 258对MTSET敏感，但对MTSES不敏感。结果表明这些氨基酸是孔衬残基。我们提出了TM VII的模型，该模型显示残基Leu 255，Leu 258，Glu 262，Asn 266和Asp 267位于TM VII的同一面附近，衬有离子转导孔。

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