Modulation of the Conductance-Voltage Relationship of the BKCa Channel by Mutations at the Putative Flexible Interface between Two RCK Domains

@article{citeulike:2814427, abstract = {Calcium-dependent gating of the large-conductance Ca2+-activated K+ (BKCa) channel is conferred by the large cytosolic carboxyl terminus containing two domains of the regulator of K+ conductance (RCK) and the high-affinity Ca2+-binding site (the Ca2+-bowl). In our previous study, we located the putative second RCK domain (RCK2) and demonstrated that it interacts directly with RCK1 via a hydrophobic "assembly interface". In this study, we tested the structural model of the other interface, the "flexible interface", by strategically positioning charge pairs across the putative interface. Several charge mutations on RCK2 affected the voltage-dependent activation of the channel. In particular, the Gly-to-Asp substitution at position 803 profoundly affected channel activation by stabilizing the open conformation of the channel with minimal effects on its Ca2+ affinity and voltage sensitivity. Various mutations at Gly-803 shifted the channel's conductance-voltage curve either left or right over a 145-mV range. Since this residue is predicted to be in the first loop of RCK2 these results strongly suggest that this loop plays a critical role in determining the intrinsic equilibrium constant for channel opening, and they support the hypothesis that this loop is part of an interface that mediates conformational coupling between RCK1 and RCK2. 10.1529/biophysj.107.108738}, author = {Kim, Hyun-Ju and Lim, Hyun-Ho and Rho, Seong-Hwan and Bao, Lin and Lee, Ju-Ho and Cox, Daniel H. and Kim, Do H. and Park, Chul-Seung }, citeulike-article-id = {2814427}, doi = {10.1529/biophysj.107.108738}, journal = {Biophys. J.}, keywords = {channels, rck}, month = {January}, number = {2}, pages = {446--456}, posted-at = {2008-05-19 23:46:35}, priority = {0}, title = {Modulation of the Conductance-Voltage Relationship of the BKCa Channel by Mutations at the Putative Flexible Interface between Two RCK Domains}, url = {http://dx.doi.org/10.1529/biophysj.107.108738}, volume = {94}, year = {2008} }

TY - JOUR ID - citeulike:2814427 L3 - citeulike-article-id:2814427 TI - Modulation of the Conductance-Voltage Relationship of the BKCa Channel by Mutations at the Putative Flexible Interface between Two RCK Domains JF - Biophys. J. VL - 94 IS - 2 SP - 446 EP - 456 N2 - Calcium-dependent gating of the large-conductance Ca2+-activated K+ (BKCa) channel is conferred by the large cytosolic carboxyl terminus containing two domains of the regulator of K+ conductance (RCK) and the high-affinity Ca2+-binding site (the Ca2+-bowl). In our previous study, we located the putative second RCK domain (RCK2) and demonstrated that it interacts directly with RCK1 via a hydrophobic "assembly interface". In this study, we tested the structural model of the other interface, the "flexible interface", by strategically positioning charge pairs across the putative interface. Several charge mutations on RCK2 affected the voltage-dependent activation of the channel. In particular, the Gly-to-Asp substitution at position 803 profoundly affected channel activation by stabilizing the open conformation of the channel with minimal effects on its Ca2+ affinity and voltage sensitivity. Various mutations at Gly-803 shifted the channel's conductance-voltage curve either left or right over a 145-mV range. Since this residue is predicted to be in the first loop of RCK2 these results strongly suggest that this loop plays a critical role in determining the intrinsic equilibrium constant for channel opening, and they support the hypothesis that this loop is part of an interface that mediates conformational coupling between RCK1 and RCK2. 10.1529/biophysj.107.108738 KW - channels KW - rck AU - Kim, Hyun-Ju AU - Lim, Hyun-Ho AU - Rho, Seong-Hwan AU - Bao, Lin AU - Lee, Ju-Ho AU - Cox, Daniel AU - Kim, Do AU - Park, Chul-Seung PY - 2008/01/15/ UR - http://dx.doi.org/10.1529/biophysj.107.108738 ER -