Calmodulin crystal structure

FIGURE 12-21 Calmodulin. This is the protein mediator of many Ca2+-stimu-lated enzymatic reactions. Calmodulin has four high-affinity Ca2+-binding sites (Kd 0.1 to 1 /cm), (a) A ribbon model of the crystal structure of calmodulin (PDB ID 1CLL). The four Ca2+-binding sites are occupied by Ca2+ (purple). 

Figure 6-8 Stereoscopic backbone trace of a 148-residue recombinant calmodulin. The two helix-tum-helix (EF-hand) loops and their bound Ca2+ (as concentric circles) are at the top and the two near the C terminus are at the bottom. The long central helix, seen in this crystal structure, may undergo conformational changes during the functioning of this Ca2+-sensing molecule.132 From Chatto-padhyaya et al.m Courtesy of F. A. Quiocho.

The E-F hand proteins parvalbumin, troponin C, calmodulin, calbindin and onco-modulin have been studied with respect to lanthanide interactions. The crystal structure of parvalbumin [82] consists of six a-helical regions labeled as A-F. One Ca2+ ion is bound in the loop joining C and D helices and the second ion in the loop of E-F. Calcium ion is bound to six protein ligands in the CD site. Ca2+ in the EF site is bound to seven protein ligands and a water molecule. 

The mechanism of calcium-induced activation of calmodulin has been and continues to be a debated topic. Since the first X-ray crystal structure of calcium-loaded calmodulin (13), models have been proposed for the structure of the apo form of calmodulin (31) based on... 

Calmodulin is a 16.8-kDa protein with a dumbbellshaped structure in which a pair of EF Ca + binding sites are contained in each lobe (Babu et al., 1988). In the crystal structure the overall length of calmodulin is 65 A, and the two lobes are connected by a seven-turn... 

FIGURE 5 View of the a-carbon backbone of calmodulin (blue) bound to calmodulin binding domain peptide (red) of smooth muscle MLCK. This view is derived from the crystal structure (Meador et al, 1992) as deposited in the Brookhaven Protein Database (reference number ICDL). The peptide includes hydrophobic residues (yellow), Trp and Leu, at its N and C termini, respectively. 

It is documented for the crystal structures of inactive human CDK2 and the partially activated human CDK2-cyclin A complex that large conformational changes of the activation segment occur [48], Comparing the position of the activation segment in the structures for Twitchin Kinase, IRK, calmodulin-depend kinase I (CaMKI), and MAPK, a variety of conformations are revealed that are accessible to different kinases in their inactive state [15, 16, 49,... 

Figure 17. Lead has been used as a heavy atom derivative to solve the phase problem in the crystal structures of a variety of protein including the calcium proteins calmodulin and synaptotagmin and die zinc protein 5-aminolevulinic acid dehydratase, ALAD. These structures provide useful insights into the coordination environments preferred by lead, which can bind both to carboxylate-rich calcium sites and thiol-rich zinc sites. Structures downloaded from die protein databank (3CLN, IRSY, 1AW5, IQNV) where necessary, lead was added to die figure based upon coordinates provided by the authors (240, 241, 243, 246). Figure adapted from Curr. Opin. Chem. Biol., Vol. 5, H.A. Godwin, The biological chemistry of lead, pp. 223-227, Copyright 2(X)1, with permission from Elsevier Science.

Xu, R.-M., Carmel, G., Sweet, R.M., Kuret, J. and Cheng, X. 1995. Crystal structure of casein kinase-1, a phosphate-directed protein kinase. EMBO J. 14 1015-1023 Yamamoto, H., Eukunaga, K., Tanaka, E. and Miyamoto, E. 1983. Ca - and calmodulin-dependent phosphorylation of microtubule-associated protein 2 and tau factor, and inhibition of microtubule assembly. J. Neurochem. 41 1119-1125 Yamamoto, H., Eukunaga, K., Goto, S., Tanaka, E. and Miyamoto, E. 1985. Ca, calmoduUn-dependent regulation of microtubule formation via phosphorylation of microtubule-assodated protein 2, tau factor, and tubiiUn, and comparison with the cyclic AMP-dependent phosphorylation. J. Neurochem. 44 759—768... 

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