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Channels (Austin). 2013 May-Jun;7(3):194-205. doi: 10.4161/chan.24492. Epub 2013 Apr 16.

SLO-2 isoforms with unique Ca(2+) - and voltage-dependence characteristics confer sensitivity to hypoxia in C. elegans.

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Department of Physiology and Biophysics, Virginia Commonwealth University, Medical College of Virginia Campus, Richmond, VA, USA.


Slo channels are large conductance K (+) channels that display marked differences in their gating by intracellular ions. Among them, the Slo1 and C. elegans SLO-2 channels are gated by calcium (Ca ( 2+) ), while mammalian Slo2 channels are activated by both sodium (Na (+) ) and chloride (Cl (-) ). Here, we report that SLO-2 channels, SLO-2a and a novel N-terminal variant isoform, SLO-2b, are activated by Ca ( 2+) and voltage, but in contrast to previous reports they do not exhibit Cl (-) sensitivity. Most importantly, SLO-2 provides a unique case in the Slo family for sensing Ca ( 2+) with the high-affinity Ca ( 2+) regulatory site in the RCK1 but not the RCK2 domain, formed through interactions with residues E319 and E487 (that correspond to D362 and E535 of Slo1, respectively). The SLO-2 RCK2 domain lacks the Ca ( 2+) bowl structure and shows minimal Ca ( 2+) dependence. In addition, in contrast to SLO-1, SLO-2 loss-of-function mutants confer resistance to hypoxia in C. elegans. Thus, the C. elegans SLO-2 channels possess unique biophysical and functional properties.


Ca2+ binding; Slo channel; allosteric regulation; ion channels; membrane function; polymerase chain reaction (PCR); protein metal ion interaction

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