6mue
From Proteopedia
Voltage-gated sodium channel NaV1.4 IQ domain in complex with Ca2+/Calmodulin
Structural highlights
DiseaseCALM1_HUMAN The disease is caused by mutations affecting the gene represented in this entry. Mutations in CALM1 are the cause of CPVT4. The disease is caused by mutations affecting the gene represented in this entry. Mutations in CALM1 are the cause of LQT14. FunctionCALM1_HUMAN Calmodulin mediates the control of a large number of enzymes, ion channels, aquaporins and other proteins through calcium-binding. Among the enzymes to be stimulated by the calmodulin-calcium complex are a number of protein kinases and phosphatases. Together with CCP110 and centrin, is involved in a genetic pathway that regulates the centrosome cycle and progression through cytokinesis (PubMed:16760425). Mediates calcium-dependent inactivation of CACNA1C (PubMed:26969752). Positively regulates calcium-activated potassium channel activity of KCNN2 (PubMed:27165696).[1] [2] [3] [4] Publication Abstract from PubMedVoltage-gated sodium (NaV) and calcium channels (CaV) form targets for calmodulin (CaM), which affects channel inactivation properties. A major interaction site for CaM resides in the C-terminal (CT) region, consisting of an IQ domain downstream of an EF-hand domain. We present a crystal structure of fully Ca(2+)-occupied CaM, bound to the CT of NaV1.5. The structure shows that the C-terminal lobe binds to a site approximately 90 degrees rotated relative to a previous site reported for an apoCaM complex with the NaV1.5 CT and for ternary complexes containing fibroblast growth factor homologous factors (FHF). We show that the binding of FHFs forces the EF-hand domain in a conformation that does not allow binding of the Ca(2+)-occupied C-lobe of CaM. These observations highlight the central role of the EF-hand domain in modulating the binding mode of CaM. The binding sites for Ca(2+)-free and Ca(2+)-occupied CaM contain targets for mutations linked to long-QT syndrome, a type of inherited arrhythmia. The related NaV1.4 channel has been shown to undergo Ca(2+)-dependent inactivation (CDI) akin to CaVs. We present a crystal structure of Ca(2+)/CaM bound to the NaV1.4 IQ domain, which shows a binding mode that would clash with the EF-hand domain. We postulate the relative reorientation of the EF-hand domain and the IQ domain as a possible conformational switch that underlies CDI. Crystal structures of Ca(2+)-calmodulin bound to NaV C-terminal regions suggest role for EF-hand domain in binding and inactivation.,Gardill BR, Rivera-Acevedo RE, Tung CC, Van Petegem F Proc Natl Acad Sci U S A. 2019 May 9. pii: 1818618116. doi:, 10.1073/pnas.1818618116. PMID:31072926[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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