A Single Amino Acid Change in CaV1.2 Channels Eliminates the Permeation and Gating Differences Between Ca2+ and Ba2+

A Single Amino Acid Change in CaV1.2 Channels Eliminates the Permeation and Gating Differences... Glutamate scanning mutagenesis was used to assess the role of the calcicludine binding segment in regulating channel permeation and gating using both Ca2+ and Ba2+ as charge carriers. As expected, wild-type CaV1.2 channels had a Ba2+ conductance ~2× that in Ca2+ (GBa/GCa = 2) and activation was ~10 mV more positive in Ca2+ vs. Ba2+. Of the 11 mutants tested, F1126E was the only one that showed unique permeation and gating properties compared to the wild type. F1126E equalized the CaV1.2 channel conductance (GBa/GCa = 1) and activation voltage dependence between Ca2+ and Ba2+. Ba2+ permeation was reduced because the interactions among multiple Ba2+ ions and the pore were specifically altered for F1126E, which resulted in Ca2+-like ionic conductance and unitary current. However, the high-affinity block of monovalent cation flux was not altered for either Ca2+ or Ba2+. The half-activation voltage of F1126E in Ba2+ was depolarized to match that in Ca2+, which was unchanged from that in the wild type. As a result, the voltages for half-activation and half-inactivation of F1126E in Ba2+ and Ca2+ were similar to those of wild-type in Ca2+. This effect was specific to F1126E since F1126A did not affect the half-activation voltage in either Ca2+ or Ba2+. These results indicate that residues in the outer vestibule of the CaV1.2 channel pore are major determinants of channel gating, selectivity, and permeation. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

A Single Amino Acid Change in CaV1.2 Channels Eliminates the Permeation and Gating Differences Between Ca2+ and Ba2+

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Copyright © 2010 by Springer Science+Business Media, LLC
Life Sciences; Human Physiology ; Biochemistry, general
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