4gow | pdb_00004gow
Crystal Structure of Ca2+/CaM:Kv7.4 (KCNQ4) B helix complex
Structural highlights
Disease[KCNQ4_HUMAN] Defects in KCNQ4 are the cause of deafness autosomal dominant type 2A (DFNA2A) [MIM:600101]. DFNA2A is a form of sensorineural hearing loss. Sensorineural deafness results from damage to the neural receptors of the inner ear, the nerve pathways to the brain, or the area of the brain that receives sound information.[1] [2] [3] [4] [5] Function[KCNQ4_HUMAN] Probably important in the regulation of neuronal excitability. May underlie a potassium current involved in regulating the excitability of sensory cells of the cochlea. KCNQ4 channels are blocked by linopirdin, XE991 and bepridil, whereas clofilium is without significant effect. Muscarinic agonist oxotremorine-M strongly suppress KCNQ4 current in CHO cells in which cloned KCNQ4 channels were coexpressed with M1 muscarinic receptors.[6] Publication Abstract from PubMedCalmodulin (CaM) is an important regulator of Kv7.x (KCNQx) voltage-gated potassium channels. Channels from this family produce neuronal M currents and cardiac and auditory I(KS) currents and harbor mutations that cause arrhythmias, epilepsy, and deafness. Despite extensive functional characterization, biochemical and structural details of the interaction between CaM and the channel have remained elusive. Here, we show that both apo-CaM and Ca(2+)/CaM bind to the C-terminal tail of the neuronal channel Kv7.4 (KCNQ4), which is involved in both hearing and mechanosensation. Interactions between apo-CaM and the Kv7.4 tail involve two C-terminal tail segments, known as the A and B segments, whereas the interaction between Ca(2+)/CaM and the Kv7.4 C-terminal tail requires only the B segment. Biochemical studies show that the calcium dependence of the CaM:B segment interaction is conserved in all Kv7 subtypes. X-ray crystallographic determination of the structure of the Ca(2+)/CaM:Kv7.4 B segment complex shows that Ca(2+)/CaM wraps around the Kv7.4 B segment, which forms an alpha-helix, in an antiparallel orientation that embodies a variation of the classic 1-14 Ca(2+)/CaM interaction motif. Taken together with the context of prior studies, our data suggest a model for modulation of neuronal Kv7 channels involving a calcium-dependent conformational switch from an apo-CaM form that bridges the A and B segments to a Ca(2+)/CaM form bound to the B-helix. The structure presented here also provides a context for a number of disease-causing mutations and for further dissection of the mechanisms by which CaM controls Kv7 function. Structure of a Ca(2+)/CaM:Kv7.4 (KCNQ4) B-Helix Complex Provides Insight into M Current Modulation.,Xu Q, Chang A, Tolia A, Minor DL Jr J Mol Biol. 2012 Nov 23. pii: S0022-2836(12)00895-9. doi:, 10.1016/j.jmb.2012.11.023. PMID:23178170[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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