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Lookup NU author(s): Dr Seva TelezhkinORCiD
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The large conductance, voltage- and calcium-activated potassium channel, BK(Ca), is a known target for the gasotransmitter, carbon monoxide (CO). Activation of BK(Ca) by CO modulates cellular excitability and contributes to the physiology of a diverse array of processes, including vascular tone and oxygen-sensing. Currently, there is no consensus regarding the molecular mechanisms underpinning reception of CO by the BK(Ca). Here, employing voltage-clamped, inside-out patches from HEK293 cells expressing single, double and triple cysteine mutations in the BK(Ca) α-subunit, we test the hypothesis that CO regulation is conferred upon the channel by interactions with cysteine residues within the RCK2 domain. In physiological [Ca(2+)](i), all mutants carrying a cysteine substitution at position 911 (C911G) demonstrated significantly reduced CO sensitivity; the C911G mutant did not express altered Ca(2+)-sensitivity. In contrast, histidine residues in RCK1 domain, previously shown to ablate CO activation in low [Ca(2+)](i), actually increased CO sensitivity when [Ca(2+)](i) was in the physiological range. Importantly, cyanide, employed here as a substituent for CO at potential metal centres, occluded activation by CO; this effect was freely reversible. Taken together, these data suggest that a specific cysteine residue in the C-terminal domain, which is close to the Ca(2+) bowl but which is not involved in Ca(2+) activation, confers significant CO sensitivity to BK(Ca) channels. The rapid reversibility of CO and cyanide binding, coupled to information garnered from other CO-binding proteins, suggests that C911 may be involved in formation of a transition metal cluster which can bind and, thereafter, activate BK(Ca).
Author(s): Telezhkin V, Brazier SP, Mears R, Müller CT, Riccardi D, Kemp PJ
Publication type: Article
Publication status: Published
Journal: Pflügers Archiv - European Journal of Physiology
Year: 2011
Volume: 461
Issue: 6
Pages: 665-675
Print publication date: 01/06/2011
Online publication date: 08/02/2011
ISSN (print): 0031-6768
ISSN (electronic): 1432-2013
Publisher: Springer
URL: http://dx.doi.org/10.1007/s00424-011-0924-7
DOI: 10.1007/s00424-011-0924-7
PubMed id: 21301863
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