6vam
Cryo-EM structure of octameric chicken CALHM1
Structural highlights
Function[GFP_AEQVI] Energy-transfer acceptor. Its role is to transduce the blue chemiluminescence of the protein aequorin into green fluorescent light by energy transfer. Fluoresces in vivo upon receiving energy from the Ca(2+)-activated photoprotein aequorin. Publication Abstract from PubMedThe biological membranes of many cell types contain large-pore channels through which a wide variety of ions and metabolites permeate. Examples include connexin, innexin and pannexin, which form gap junctions and/or bona fide cell surface channels. The most recently identified large-pore channels are the calcium homeostasis modulators (CALHMs), through which ions and ATP permeate in a voltage-dependent manner to control neuronal excitability, taste signaling and pathologies of depression and Alzheimer's disease. Despite such critical biological roles, the structures and patterns of their oligomeric assembly remain unclear. Here, we reveal the structures of two CALHMs, chicken CALHM1 and human CALHM2, by single-particle cryo-electron microscopy (cryo-EM), which show novel assembly of the four transmembrane helices into channels of octamers and undecamers, respectively. Furthermore, molecular dynamics simulations suggest that lipids can favorably assemble into a bilayer within the larger CALHM2 pore, but not within CALHM1, demonstrating the potential correlation between pore size, lipid accommodation and channel activity. Structure and assembly of calcium homeostasis modulator proteins.,Syrjanen JL, Michalski K, Chou TH, Grant T, Rao S, Simorowski N, Tucker SJ, Grigorieff N, Furukawa H Nat Struct Mol Biol. 2020 Feb;27(2):150-159. doi: 10.1038/s41594-019-0369-9. Epub, 2020 Jan 27. PMID:31988524[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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