Critical loci for ion conduction in inward rectifier K+ channels are only now being discovered. The C-terminal region of IRK1 plays a crucial role in Mg2+i blockade and single-channel K+ conductance. A negatively charged aspartate in the putative second transmembrane domain (position 172) is essential for time-dependent block by the cytoplasmic polyamines spermine and spermidine. We have now localized the C-terminus effect in IRK1 to a single, negatively charged residue (E224). Mutation of E224 to G, Q and S drastically reduced rectification. Furthermore, the IRK1 E224G mutation decreased block by Mg2+i and spermidine and, like the E224Q mutation, caused a dramatic reduction in the apparent single-channel K+ conductance. The double mutation IRK1 D172N+ E224G was markedly insensitive to spermidine block, displaying an affinity similar to ROMK1. The results are compatible with a model in which the negatively charged residue at position 224, E224, is a major determinant of pore properties in IRK1. By means of a specific interaction with the negatively charged residue at position 172, D172, E224 contributes to the formation of the binding pocket for Mg2+ and polyamines, a characteristic of strong inward rectifiers.
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http://dx.doi.org/10.1002/j.1460-2075.1995.tb00240.x | DOI Listing |
Nat Mater
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Laboratory of Advanced Optoelectronic Materials, Suzhou Key Laboratory of Novel Semiconductor-optoelectronics Materials and Devices, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, China.
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State Key Laboratory of Precision Manufacturing for Extreme Service Performance, College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China; Jiangxi Province Key Laboratory of Additive Manufacturing of Implantable Medical Device, Jiangxi University of Science and Technology, Nanchang 330013, China. Electronic address:
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Unit of Biophysics, Department of Biochemistry and Molecular Biology, Facultat de Medicina, Av. Can Domènech s/n, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Catalonia, Spain.
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View Article and Find Full Text PDFPLoS One
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School of Economics and Management, Shanghai Maritime University, Shanghai, China.
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