NDLI: Allosteric effects of external K+ ions mediated by the aspartate of the GYGD signature sequence in the Kv2.1 K+ channel

Content Provider	Springer Nature Link
Author	Chapman, Mark L. Blanke, Marie L. Krovetz, Howard S. VanDongen, Antonius M.J.
Copyright Year	2005
Abstract	K+ channels achieve exquisite ion selectivity without jeopardizing efficient permeation by employing multiple, interacting K+-binding sites. Introduction of a cadmium (Cd2+)-binding site in the external vestibule of Kv2.1 (drk1), allowed us to functionally characterize a binding site for external monovalent cations. Permeant ions displayed higher affinity for this site than non-permeant monovalent cations, although the selectivity profile was different from that of the channel. Point mutations identified the highly conserved aspartate residue immediately following the selectivity filter as a critical determinant of the antagonism between external K+ and Cd2+ ions. A conservative mutation at this position (D378E) significantly affected the open-state stability. Moreover, the mean open time was found to be modulated by external K+ concentration, suggesting a coupling between channel closing and the permeation process. Reducing the Rb+ conductance by mutating the selectivity filter to the sequence found in Kv4.1, also significantly reduced the effectiveness of Rb+ ions to antagonize Cd2+ inhibition, thereby implicating the selectivity filter as the site at which K+ ions exert their antagonistic effect on Cd2+ block. The equivalent of D378 in KcsA, D80, takes part in an inter-subunit hydrogen-bond network that allows D80 to functionally interact with the selectivity filter. The results suggest that external K+ ions antagonize Cd2+ inhibition (in I379C) and modulate the mean open time (in the wild-type Kv2.1) by altering the occupancy profile of the K+-binding sites in the selectivity filter.
Starting Page	776
Ending Page	792
Page Count	17
File Format	PDF
ISSN	00316768
Journal	Pflügers Archiv
Volume Number	451
Issue Number	6
e-ISSN	14322013
Language	English
Publisher	Springer-Verlag
Publisher Date	2005-11-10
Publisher Place	Berlin, Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Content Type	Text
Resource Type	Article
Subject	Physiology Physiology (medical) Clinical Biochemistry

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