The RCK2 domain uses a coordination site present in Kir channels to confer sodium sensitivity to Slo2.2 channels.
Slo2 Na(+)-activated potassium channels are widely expressed in neurons and other cells, such as kidney, heart, and skeletal muscle. Although their important physiological roles continue to be appreciated, molecular determinants responsible for sensing intracellular Na(+) remain unknown. Here we report identification of an Na(+) regulatory site, similar to an Na(+) coordination motif described in Kir channels, localized in the RCK2 domain of Slo2.2 channels. Molecular simulations of the homology-modeled Slo2.2 RCK2 domain provided structural insights into the organization of this Na(+) coordination site. Furthermore, free energy calculations reproduced the experimentally derived monovalent cation selectivity. Our results suggest that Slo2.2 and Kir channels share a similar mechanism to coordinate Na(+). The localization of an Na(+) sensor within the RCK2 domain of Slo2.2 further supports the role of RCK (regulators of conductance of K(+)) domains of Slo channels in coupling ion sensing to channel gating.
Department of Physiology and Biophysics, Virginia Commonwealth University, School of Medicine, Richmond, Virginia 23298-0551, USA.
Zhe
Z
Zhang
Avia
A
Rosenhouse-Dantsker
Qiong-Yao
QY
Tang
Sergei
S
Noskov
Diomedes E
DE
Logothetis
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000235:genetics; D000818:Animals; D055592:Biophysical Phenomena / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D002712:Chlorides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000235:genetics / Q000378:metabolism; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics; D051667:Kv1.6 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008845:Microinjections / Q000379:methods; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009865:Oocytes; D018408:Patch-Clamp Techniques; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D014982:Xenopus laevis
D000596:Amino Acids; D002712:Chlorides; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D051667:Kv1.6 Potassium Channel; D012964:Sodium