Structural highlights
Function[AT2A1_RABIT] This magnesium-dependent enzyme catalyzes the hydrolysis of ATP coupled with the translocation of calcium from the cytosol to the sarcoplasmic reticulum lumen. Contributes to calcium sequestration involved in muscular excitation/contraction (By similarity). Publication Abstract from PubMedThe sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) couples ATP hydrolysis to transport of Ca(2+). This directed energy transfer requires cross-talk between the two Ca(2+) sites and the phosphorylation site over 50 A distance. We have addressed the mechano-structural basis for this intramolecular signal by analysing the structure and the functional properties of SERCA mutant E309Q. Glu(309) contributes to Ca(2+) coordination at site II, and a consensus has been that E309Q only binds Ca(2+) at site I. The crystal structure of E309Q in the presence of Ca(2+) and an ATP analogue, however, reveals two occupied Ca(2+) sites of a non-catalytic Ca2E1 state. Ca(2+) is bound with micromolar affinity by both Ca(2+) sites in E309Q, but without cooperativity. The Ca(2+)-bound mutant does phosphorylate from ATP, but at a very low maximal rate. Phosphorylation depends on the correct positioning of the A-domain, requiring a shift of transmembrane segment M1 into an 'up and kinked position'. This transition is impaired in the E309Q mutant, most likely due to a lack of charge neutralization and altered hydrogen binding capacities at Ca(2+) site II. SERCA mutant E309Q binds two Ca(2+) ions but adopts a catalytically incompetent conformation.,Clausen JD, Bublitz M, Arnou B, Montigny C, Jaxel C, Moller JV, Nissen P, Andersen JP, le Maire M EMBO J. 2013 Dec 11;32(24):3231-43. doi: 10.1038/emboj.2013.250. Epub 2013 Nov, 22. PMID:24270570[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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