TY - JOUR
T1 - Structure and function of multiple Ca 2+-binding sites in a K + channel regulator of K + conductance (RCK) domain
AU - Pau, Victor P.T.
AU - Smith, Frank J.
AU - Taylor, Alexander B.
AU - Parfenova, Liubov V.
AU - Samakai, Elsie
AU - Callaghan, Matthew M.
AU - Abarca-Heidemann, Karin
AU - Hart, P. John
AU - Rothberg, Brad S.
PY - 2011/10/25
Y1 - 2011/10/25
N2 - Regulator of K + conductance (RCK) domains control the activity of a variety of K + transporters and channels, including the human large conductance Ca 2+-activated K + channel that is important for blood pressure regulation and control of neuronal firing, and MthK, a prokaryotic Ca 2+-gated K + channel that has yielded structural insight toward mechanisms of RCK domain-controlled channel gating. In MthK, a gating ring of eight RCK domains regulates channel activation by Ca 2+. Here, using electrophysiology and X-ray crystallography, we show that each RCK domain contributes to three different regulatory Ca 2+-binding sites, two of which are located at the interfaces between adjacent RCK domains. The additional Ca 2+-binding sites, resulting in a stoichiometry of 24 Ca 2+ ions per channel, is consistent with the steep relation between [Ca 2+] and MthK channel activity. Comparison of Ca 2+-bound and unliganded RCK domains suggests a physical mechanism for Ca 2+-dependent conformational changes that underlie gating in this class of channels.
AB - Regulator of K + conductance (RCK) domains control the activity of a variety of K + transporters and channels, including the human large conductance Ca 2+-activated K + channel that is important for blood pressure regulation and control of neuronal firing, and MthK, a prokaryotic Ca 2+-gated K + channel that has yielded structural insight toward mechanisms of RCK domain-controlled channel gating. In MthK, a gating ring of eight RCK domains regulates channel activation by Ca 2+. Here, using electrophysiology and X-ray crystallography, we show that each RCK domain contributes to three different regulatory Ca 2+-binding sites, two of which are located at the interfaces between adjacent RCK domains. The additional Ca 2+-binding sites, resulting in a stoichiometry of 24 Ca 2+ ions per channel, is consistent with the steep relation between [Ca 2+] and MthK channel activity. Comparison of Ca 2+-bound and unliganded RCK domains suggests a physical mechanism for Ca 2+-dependent conformational changes that underlie gating in this class of channels.
KW - Calcium
KW - Cooperativity
KW - Lipid bilayer
UR - http://www.scopus.com/inward/record.url?scp=80055074900&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=80055074900&partnerID=8YFLogxK
U2 - 10.1073/pnas.1107229108
DO - 10.1073/pnas.1107229108
M3 - Article
C2 - 21997217
AN - SCOPUS:80055074900
SN - 0027-8424
VL - 108
SP - 17684
EP - 17689
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 43
ER -