Van Petegem Filip, Chatelain Franck C, Minor Daniel L
Cardiovascular Research Institute, Department of Biochemistry and Biophysics, California Institute for Quantitative Biomedical Research, University of California, San Francisco, 1700 4th St., Box 2532, San Francisco, California 94143-2532, USA.
Nat Struct Mol Biol. 2005 Dec;12(12):1108-15. doi: 10.1038/nsmb1027. Epub 2005 Nov 20.
Changes in activity-dependent calcium flux through voltage-gated calcium channels (Ca(V)s) drive two self-regulatory calcium-dependent feedback processes that require interaction between Ca(2+)/calmodulin (Ca(2+)/CaM) and a Ca(V) channel consensus isoleucine-glutamine (IQ) motif: calcium-dependent inactivation (CDI) and calcium-dependent facilitation (CDF). Here, we report the high-resolution structure of the Ca(2+)/CaM-Ca(V)1.2 IQ domain complex. The IQ domain engages hydrophobic pockets in the N-terminal and C-terminal Ca(2+)/CaM lobes through sets of conserved 'aromatic anchors.' Ca(2+)/N lobe adopts two conformations that suggest inherent conformational plasticity at the Ca(2+)/N lobe-IQ domain interface. Titration calorimetry experiments reveal competition between the lobes for IQ domain sites. Electrophysiological examination of Ca(2+)/N lobe aromatic anchors uncovers their role in Ca(V)1.2 CDF. Together, our data suggest that Ca(V) subtype differences in CDI and CDF are tuned by changes in IQ domain anchoring positions and establish a framework for understanding CaM lobe-specific regulation of Ca(V)s.
通过电压门控钙通道（Ca(V)s）的活动依赖性钙通量变化驱动了两个自我调节的钙依赖性反馈过程，这两个过程需要Ca(2+)/钙调蛋白（Ca(2+)/CaM）与Ca(V)通道共有异亮氨酸 - 谷氨酰胺（IQ）基序之间相互作用：钙依赖性失活（CDI）和钙依赖性易化（CDF）。在此，我们报道了Ca(2+)/CaM - Ca(V)1.2 IQ结构域复合物的高分辨率结构。IQ结构域通过一组保守的“芳香族锚定物”与N端和C端Ca(2+)/CaM叶中的疏水口袋结合。Ca(2+)/N叶采用两种构象，这表明在Ca(2+)/N叶 - IQ结构域界面处存在固有的构象可塑性。滴定热分析实验揭示了两个叶之间对IQ结构域位点的竞争。对Ca(2+)/N叶芳香族锚定物的电生理检查揭示了它们在Ca(V)1.2 CDF中的作用。总之，我们的数据表明，CDI和CDF中Ca(V)亚型的差异是由IQ结构域锚定位置的变化调节的，并建立了一个理解CaM叶对Ca(V)s特异性调节的框架。
