Portal de Periódicos da CAPES

Crystal Structure of a Ba2+-Bound Gating Ring Reveals Elementary Steps in RCK Domain Activation

2012; Elsevier BV; Volume: 20; Issue: 12 Linguagem: Inglês

10.1016/j.str.2012.09.014

1878-4186

Frank J. Smith, Victor P.T. Pau, Gino Cingolani, Brad S. Rothberg,

Neuroscience and Neuropharmacology Research

RCK domains control activity of a variety of K+ channels and transporters through binding of cytoplasmic ligands. To gain insight toward mechanisms of RCK domain activation, we solved the structure of the RCK domain from the Ca2+-gated K+ channel, MthK, bound with Ba2+, at 3.1 Å resolution. The Ba2+-bound RCK domain was assembled as an octameric gating ring, as observed in structures of the full-length MthK channel, and shows Ba2+ bound at several positions. One of the Ba2+ sites, termed C1, overlaps with a known Ca2+-activation site, determined by residues D184 and E210. Functionally, Ba2+ can activate reconstituted MthK channels as observed in electrophysiological recordings, whereas Mg2+ (up to 100 mM) was ineffective. Ba2+ activation was abolished by the mutation D184N, suggesting that Ba2+ activates primarily through the C1 site. Our results suggest a working hypothesis for a sequence of ligand-dependent conformational changes that may underlie RCK domain activation and channel gating.