Crystallization extracellular

Leucine residues 2, 5, 7, 12, 20, and 24 of the motif are invariant in both type A and type B repeats of the ribonuclease inhibitor. An examination of more than 500 tandem repeats from 68 different proteins has shown that residues 20 and 24 can be other hydrophobic residues, whereas the remaining four leucine residues are present in all repeats. On the basis of the crystal structure of the ribonuclease inhibitor and the important structural role of these leucine residues, it has been possible to construct plausible structural models of several other proteins with leucine-rich motifs, such as the extracellular domains of the thyrotropin and gonadotropin receptors. 

The prolactin receptor, PER, which regulates milk production in mammals, belongs to the same receptor class as the growth hormone receptor. In addition to binding the hormone prolactin, PER also binds and is activated by growth hormone. The extracellular domain of PER forms a very stable 1 1 complex with growth hormone in solution this complex has been crystallized and its structure determined (Figure 13.21). We shall compare this structure with the 1 2 complex of the same hormone with GHR. 

De Vos, A.M., Ultsch, M., Kossiakoff, A.A. Human growth hormone and extracellular domain of its receptor crystal structure of the complex. Science 255 306-312,... 

Figure 17.12 Ribbon diagram of EMPl bound to the extracellular domain of the erythropoietin receptor (EBP). Binding of EMPl causes dimerization of erythropoietin receptor. The x-ray crystal structure of the EMPl-EBP complex shows a nearly symmetrical dimer complex in which both peptide monomers interact with both copies of EBP. Recognition between the EMPl peptides and EBP utilizes more than 60% of the EMPl surface and four of six loops in the erythropoietin-binding pocket of EBP.

S. L, Arnaout, M. A. Crystal struemre of the extracellular segment of integrin OvPs in complex with an Arg-Gly-Asp ligand. Science 2002, 296,151-155. 

FIGURE 56-1. Synovial fluid containing extracellular and intracellular monosodium urate crystals. (From Reginato AJ. Gout and other crystal arthropathies. In Braunwald E,... 

Erythropoietin is a glycoprotein hormone that regulates the proliferation, differentiation, and maturation of erythroid cells. The EPO receptor is a member of the class 1 cytokine receptor superfamily. The crystal structure of an EPO-mimetic peptide and the extracellular portion of the... 

Figure 36 Schematic representation of dynamic picture of bR in monomer. See the correlation times for the cytoplasmic and extracellular loops and transmembrane a-helices are significantly shortened as compared with those in 2D crystal as shown in Figure 24.

Ogiso H, Ishitani R, Nureki O, Fukai S, Yamanaka M, Kim J-H, Saito K, Sakamoto A, Inoue M, Shirouzu M, Yokoyama S (2002) Crystal structure of the complex of human epidermal growth factor and receptor extracellular domains. Cell 110 775-787... 

Once the pore is open, K+ ions appear to move outward in single file. Analysis of crystals shows four K+ ions interacting with the backbone carbonyl groups of the amino acid residues that form the ion selectivity filter (Fig. 6-8B). It is thought that two K+ ions occupy sites 1 and 3 (Fig. 6-8B, orange) and then switch to sites 2 and 4 (gray). The K+ ion in site 4 would dissociate into the extracellular space, the K+ ion in site 2 would move to site 3 and another... 

A recent crystal structure based model [20] for the structure of C-cadherin postulates that the five extracellular domains EC1-EC5 protrude from the cell surface as a curved rod. The structural analysis of C-cadherin reveals that the molecules facing each other across apposed cell surfaces are antiparallel to one another, forming a dimeric interaction termed a strand dimer (Fig. 7-5). This forms the functional unit that is likely to mediate adhesion between cell surfaces. The structure from this recent paper allows the prediction of both cis and trans interfaces that together result in a lattice and not, as previously believed, an adhesion zipper. This new model allows for a mechanism by which adhesion plates or puncta might be generated, such as are formed at CNS synapses [21, 22], adherens junctions and desmosomes [23], all cadherin based organelles. 

The crystal structure of the extracellular domain of P0 has also been determined [41]. The arrangement of molecules in the crystal indicates that P0 may exist on the membrane surface as a tetramer (Fig. 7-7) that can link to other tetramers from the opposing membrane to form an adhesive lattice, like a molecular Velcro . The structure also suggests that P0 mediates adhesion through the direct interaction of apically directed tryptophan side chains with the opposing membrane [42], in addition to homo-philic protein-protein interaction. 

Shapiro, L., Doyle, J. P., Hensley, P., Colman, D. R. and Hendrickson, W. A. Crystal structure of the extracellular domain from P0, the major structural protein of peripheral nerve myelin. Neuron 17 435-449,1996. 

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