5tjb
I-II linker of TRPML1 channel at pH 4.5
Structural highlights
DiseaseMCLN1_HUMAN Mucolipidosis type 4. The disease is caused by mutations affecting the gene represented in this entry. FunctionMCLN1_HUMAN Cation channel probably playing a role in the endocytic pathway and in the control of membrane trafficking of proteins and lipids. Could play a major role in Ca(2+) transport regulating lysosomal exocytosis.[1] [2] Publication Abstract from PubMedThe activities of organellar ion channels are often regulated by Ca2+ and H+, which are present in high concentrations in many organelles. Here we report a structural element critical for dual Ca2+/pH regulation of TRPML1, a Ca2+-release channel crucial for endolysosomal function. TRPML1 mutations cause mucolipidosis type IV (MLIV), a severe lysosomal storage disorder characterized by neurodegeneration, mental retardation and blindness. We obtained crystal structures of the 213-residue luminal domain of human TRPML1 containing three missense MLIV-causing mutations. This domain forms a tetramer with a highly electronegative central pore formed by a novel luminal pore loop. Cysteine cross-linking and cryo-EM analyses confirmed that this architecture occurs in the full-length channel. Structure-function studies demonstrated that Ca2+ and H+ interact with the luminal pore and exert physiologically important regulation. The MLIV-causing mutations disrupt the luminal-domain structure and cause TRPML1 mislocalization. Our study reveals the structural underpinnings of TRPML1's regulation, assembly and pathogenesis. Structural basis of dual Ca2+/pH regulation of the endolysosomal TRPML1 channel.,Li M, Zhang WK, Benvin NM, Zhou X, Su D, Li H, Wang S, Michailidis IE, Tong L, Li X, Yang J Nat Struct Mol Biol. 2017 Mar;24(3):205-213. doi: 10.1038/nsmb.3362. Epub 2017, Jan 23. PMID:28112729[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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