3o78

The structure of Ca2+ Sensor (Case-12)

spinqualitylabelsall models 3o78, resolution 2.60Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3o78 is a 2 chain structure. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CA NonStd Res: CR2 Related: 3o77, 3ek4, 3ek7, 3ek8, 3ekh, 3ekj, 3evp, 3evr, 3evu, 3evv Activity: [Myosin_light-chain_kinase [Myosin light-chain] kinase], with EC number 2.7.11.18 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [MYLK_CHICK] Phosphorylates a specific serine in the N-terminus of a myosin light chain, which leads to the formation of calmodulin/MLCK signal transduction complexes which allow selective transduction of calcium signals. Publication Abstract from PubMed Here we report the first crystal structure of a high-contrast genetically encoded circularly permuted green fluorescent protein (cpGFP)-based Ca(2+) sensor, Case16, in the presence of a low Ca(2+) concentration. The structure reveals the positioning of the chromophore within Case16 at the first stage of the Ca(2+)-dependent response when only two out of four Ca(2+)-binding pockets of calmodulin (CaM) are occupied with Ca(2+) ions. In such a "half Ca(2+)-bound state", Case16 is characterized by an incomplete interaction between its CaM-/M13-domains. We also report the crystal structure of the related Ca(2+) sensor Case12 at saturating Ca(2+) concentration. Based on this structure, we postulate that cpGFP-based Ca(2+) sensors can form non-functional homodimers where the CaM-domain of one sensor molecule binds symmetrically to the M13-peptide of the partner sensor molecule. Case12 and Case16 behavior upon addition of high concentrations of free CaM or M13-peptide reveals that the latter effectively blocks the fluorescent response of the sensor. We speculate that the demonstrated intermolecular interaction with endogenous substrates and homodimerization can impede proper functioning of this type of Ca(2+) sensors in living cells. The structure of Ca2+ sensor Case16 reveals the mechanism of reaction to low Ca2+ concentrations.,Leder L, Stark W, Freuler F, Marsh M, Meyerhofer M, Stettler T, Mayr LM, Britanova OV, Strukova LA, Chudakov DM, Souslova EA Sensors (Basel). 2010;10(9):8143-60. Epub 2010 Aug 30. PMID:22163646 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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