NDLI: The RCK2 domain of the human BKCa channel is a calcium sensor

Content Provider	PubMed Central
Author	Yusifov, Taleh Nicoletta, Savalli Gandhi, Chris S. Michela, Ottolia Olcese, Riccardo
Copyright Year	2007
Abstract	Large conductance voltage and Ca2+-dependent K+ channels (BKCa) are activated by both membrane depolarization and intracellular Ca2+. Recent studies on bacterial channels have proposed that a Ca2+-induced conformational change within specialized regulators of K+ conductance (RCK) domains is responsible for channel gating. Each pore-forming α subunit of the homotetrameric BKCa channel is expected to contain two intracellular RCK domains. The first RCK domain in BKCa channels (RCK1) has been shown to contain residues critical for Ca2+ sensitivity, possibly participating in the formation of a Ca2+-binding site. The location and structure of the second RCK domain in the BKCa channel (RCK2) is still being examined, and the presence of a high-affinity Ca2+-binding site within this region is not yet established. Here, we present a structure-based alignment of the C terminus of BKCa and prokaryotic RCK domains that reveal the location of a second RCK domain in human BKCa channels (hSloRCK2). hSloRCK2 includes a high-affinity Ca2+-binding site (Ca bowl) and contains similar secondary structural elements as the bacterial RCK domains. Using CD spectroscopy, we provide evidence that hSloRCK2 undergoes a Ca2+-induced change in conformation, associated with an α-to-β structural transition. We also show that the Ca bowl is an essential element for the Ca2+-induced rearrangement of hSloRCK2. We speculate that the molecular rearrangements of RCK2 likely underlie the Ca2+-dependent gating mechanism of BKCa channels. A structural model of the heterodimeric complex of hSloRCK1 and hSloRCK2 domains is discussed.
Related Links	http://dx.doi.org/10.1073/pnas.0705261105
Ending Page	381
Page Count	6
Starting Page	376
File Format	PDF
ISSN	00278424
e-ISSN	10916490
Journal	Proceedings of the National Academy of Sciences of the United States of America
Issue Number	1
Volume Number	105
Language	English
Publisher	National Academy of Sciences
Publisher Date	2008-01-08
Access Restriction	Open
Rights Holder	National Academy of Sciences
Subject Keyword	General Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Multidisciplinary

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