期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 288, 期 20, 页码 14080-14086出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M113.457952
关键词
-
资金
- National Institutes of Health [GM38361]
Members of the Amt family of channels mediate the transport of ammonium. The form of ammonium, NH3 or NH4+, carried by these proteins remains controversial, and the mechanism by which they select against K+ ions is unclear. We describe here a set of Escherichia coli AmtB proteins carrying mutations at the conserved twin-histidine site within the conduction pore that have altered substrate specificity and now transport K+. Subsequent work established that AmtB-mediated K+ uptake occurred against a concentration gradient and was membrane potential-dependent. These findings indicate that the twin-histidine element serves as a filter to prevent K+ conduction and strongly support the notion that Amt proteins transport cations (NH4+ or, in mutant proteins, K+) rather than NH3 gas molecules through their conduction pores.
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