The RCK1 domain of the human BKCa channel transduces Ca2+ binding into structural rearrangements.
Large-conductance voltage- and Ca(2+)-activated K(+) (BK(Ca)) channels play a fundamental role in cellular function by integrating information from their voltage and Ca(2+) sensors to control membrane potential and Ca(2+) homeostasis. The molecular mechanism of Ca(2+)-dependent regulation of BK(Ca) channels is unknown, but likely relies on the operation of two cytosolic domains, regulator of K(+) conductance (RCK)1 and RCK2. Using solution-based investigations, we demonstrate that the purified BK(Ca) RCK1 domain adopts an alpha/beta fold, binds Ca(2+), and assembles into an octameric superstructure similar to prokaryotic RCK domains. Results from steady-state and time-resolved spectroscopy reveal Ca(2+)-induced conformational changes in physiologically relevant [Ca(2+)]. The neutralization of residues known to be involved in high-affinity Ca(2+) sensing (D362 and D367) prevented Ca(2+)-induced structural transitions in RCK1 but did not abolish Ca(2+) binding. We provide evidence that the RCK1 domain is a high-affinity Ca(2+) sensor that transduces Ca(2+) binding into structural rearrangements, likely representing elementary steps in the Ca(2+)-dependent activation of human BK(Ca) channels.
Yusifov
Taleh
T
Division of Molecular Medicine, Department of Anesthesiology, David Geffen School of Medicine at University of California, Los Angeles, CA 90095, USA.
Javaherian
Anoosh D
AD
Pantazis
Antonios
A
Gandhi
Chris S
CS
Olcese
Riccardo
R
D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology; D051662:Kv1.1 Potassium Channel / Q000737:chemistry; D051667:Kv1.6 Potassium Channel / Q000737:chemistry; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D008969:Molecular Sequence Data; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D044169:Receptors, Calcium-Sensing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
C494841:KCNMA1 protein, human; D051667:Kv1.6 Potassium Channel; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D044169:Receptors, Calcium-Sensing; D051662:Kv1.1 Potassium Channel; D002118:Calcium