1a29
CALMODULIN COMPLEXED WITH TRIFLUOPERAZINE (1:2 COMPLEX)
Structural highlights
FunctionCALM_BOVIN Calmodulin mediates the control of a large number of enzymes, ion channels and other proteins by Ca(2+). Among the enzymes to be stimulated by the calmodulin-Ca(2+) complex are a number of protein kinases and phosphatases. Together with CEP110 and centrin, is involved in a genetic pathway that regulates the centrosome cycle and progression through cytokinesis (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe modulatory action of Ca2+-calmodulin on multiple targets is inhibited by trifluoperazine, which competes with target proteins for calmodulin binding. The structure of calmodulin crystallized with two trifluoperazine molecules is determined by X-ray crystallography at 2.74 A resolution. The X-ray data together with the characteristic and distinct signals obtained by circular dichroism in solution allowed us to identify the binding domains as well as the order of the binding of two trifluoperazine molecules to calmodulin. Accordingly, the binding of trifluperazine to the C-terminal hydrophobic pocket is followed by the interaction of the second drug molecule with an interdomain site. Recently, we demonstrated that the two bisindole derivatives, vinblastine and KAR-2 [3"-(beta-chloroethyl)-2",4"-dioxo-3, 5"-spirooxazolidino-4-deacetoxyvinblastine], interact with calmodulin with comparable affinity; however, they display different functional effects [Orosz et al. (1997) British J. Pharmacol. 121, 955-962]. The structural basis responsible for these effects were investigated by circular dichroism and fluorescence spectroscopy. The data provide evidence that calmodulin can simultaneously accommodate trifluoperazine and KAR-2 as well as vinblastine and KAR-2, but not trifluoperazine and vinblastine. The combination of the binding and structural data suggests that distinct binding sites exist on calmodulin for vinblastine and KAR-2 which correspond, at least partly, to that of trifluoperazine at the C-terminal hydrophobic pocket and at an interdomain site, respectively. This structural arrangement can explain why these drugs display different anticalmodulin activities. Calmodulin complexed with melittin is also able to bind two trifluoperazine molecules, the binding of which appears to be cooperative. Results obtained with intact and proteolytically cleaved calmodulin reveal that the central linker region of the protein is indispensable for simultanous interactions with two molecules of either identical or different ligands. Simultaneous binding of drugs with different chemical structures to Ca2+-calmodulin: crystallographic and spectroscopic studies.,Vertessy BG, Harmat V, Bocskei Z, Naray-Szabo G, Orosz F, Ovadi J Biochemistry. 1998 Nov 3;37(44):15300-10. PMID:9799490[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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