5xab
From Proteopedia
Complete structure factors and an atomic model of the calcium pump (SERCA1A) and associated phospholipids in the E2(TG) crystals
Structural highlights
FunctionAT2A1_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 lipid bilayer has so far eluded visualization by conventional crystallographic methods, severely limiting our understanding of phospholipid- and protein-phospholipid interactions. Here we describe electron density maps for crystals of Ca2+-ATPase in four different states obtained by X-ray solvent contrast modulation. These maps resolve the entire first layer of phospholipids surrounding the transmembrane helices, although less than half of them are hydrogen-bonded to protein residues. Phospholipids follow the movements of associated residues, causing local distortions and changes in thickness of the bilayer. Unexpectedly, the entire protein tilts during the reaction cycle, governed primarily by a belt of Trp residues, to minimize energy costs accompanying the large perpendicular movements of the transmembrane helices. A class of Arg residues extend their side chains through the cytoplasm to exploit phospholipids as anchors for conformational switching. Thus, phospholipid-Arg/Lys and phospholipid-Trp interactions have distinct functional roles in the dynamics of ion pumps and, presumably, membrane proteins in general. Protein-phospholipid interplay revealed with crystals of a calcium pump.,Norimatsu Y, Hasegawa K, Shimizu N, Toyoshima C Nature. 2017 May 11;545(7653):193-198. doi: 10.1038/nature22357. Epub 2017 May 3. PMID:28467821[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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