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Tetrameric Complexes (tetrameric + complex)
Selected AbstractsA role for protein kinase CK2 in plant development: evidence obtained using a dominant-negative mutantTHE PLANT JOURNAL, Issue 1 2008Jordi Moreno-Romero Summary Protein kinase CK2 is an evolutionary conserved Ser/Thr phosphotransferase composed of two distinct subunits, , (catalytic) and , (regulatory), that combine to form a tetrameric complex. Plant genomes contain multiple genes for each subunit, the expression of which gives rise to different active holoenzymes. In order to study the effects of loss of function of CK2 on plant development, we have undertaken a dominant-negative mutant approach. We generated an inactive catalytic subunit by site-directed mutagenesis of an essential lysine residue. The mutated open reading frame was cloned downstream of an inducible promoter, and stably transformed Arabidopsis thaliana plants and tobacco BY2 cells were isolated. Continuous expression of the CK2 kinase-inactive subunit did not prevent seed germination, but seedlings exhibited a strong phenotype, affecting chloroplast development, cotyledon expansion, and root and shoot growth. Prolonged induction of the transgene was lethal. Moreover, dark-germinated seedlings exhibited an apparent de-etiolated phenotype that was not caused by disruption of the light-signalling pathways. Short-term induction of the CK2 kinase-inactive subunit allowed plant survival, but root growth and lateral root formation were significantly affected. The expression pattern of CYCB1;1::GFP in the root meristems of mutant plants demonstrated an important decrease of mitotic activity, and expression of the CK2 kinase-inactive subunit in stably transformed BY2 cells provoked perturbation of the G1/S and G2 phases of the cell cycle. Our results are consistent with a model in which CK2 plays a key role in cell division and cell expansion, with compelling effects on Arabidopsis development. [source] [CuII4] Clusters From the Self-Assembly of Two Imidazolidinyl 2-Phenolate-Bridged [CuII2] Units: The Role of the Chloride BridgeEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2007Alok Ranjan Paital Abstract A new family of tetracopper clusters [Cu4(,4 -X)L2]ClO4·nH2O (1a,c) [X = Cl, Br, I; n = 12, 2, 2; H3L = 2-(2,-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine] have been synthesised and characterised. The X-ray crystal structure of 1a reveals that the template action of the spherical Cl, anion (,4 -Cl,), which features a unique rectangular planar bridging mode, is responsible for the self-assembly of two [Cu2L]+ units in complex 1a. In this family of complexes the spherical halides serve as templates to assemble the dimeric unit into tetrameric complexes, which gives an insight into the role of the halide bridge in tetranuclear complex formation. The capacity of this bridge to mediate magnetic coupling has been examined by bulk magnetic measurements for complex 1a. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Comparison of GFL,GFR, complexes: further evidence relating GFL bend angle to RET signallingACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2009Vimal Parkash Glial cell line-derived neurotrophic factor (GDNF) activates the receptor tyrosine kinase RET by binding to the GDNF-family receptor ,1 (GFR,1) and forming the GDNF2,GFR,12,RET2 heterohexamer complex. A previous crystal structure of the GDNF2,GFR,12 complex (PDB code 2v5e) suggested that differences in signalling in GDNF-family ligand (GFL) complexes might arise from differences in the bend angle between the two monomers in the GFL homodimer. Here, a 2.35,Å resolution structure of the GDNF2,GFR,12 complex crystallized with new cell dimensions is reported. The structure was refined to a final R factor of 22.5% (Rfree = 28%). The structures of both biological tetrameric complexes in the asymmetric unit are very similar to 2v5e and different from the artemin,GFR,3 structure, even though there is a small change in the structure of the GDNF. By comparison of all known GDNF and artemin structures, it is concluded that GDNF is more bent and more flexible than artemin and that this may be related to RET signalling. Comparisons also suggest that the differences between artemin and GDNF arise from the increased curvature of the artemin `fingers', which both increases the buried surface area in the monomer,monomer interface and changes the intermonomer bend angle. From sequence comparison, it is suggested that neuturin (the second GFL) adopts an artemin-like conformation, while persephin has a different conformation to the other three. [source] Filaggrin null mutations associate with increased frequencies of allergen-specific CD4+ T-helper 2 cells in patients with atopic eczemaBRITISH JOURNAL OF DERMATOLOGY, Issue 3 2010T. McPherson Summary Background, Filaggrin null mutations associate with atopic eczema and also with asthma when present with eczema. However, while epidermal dysfunction is an important factor in disease pathogenesis, it is unclear how such dysfunction interacts with immune responses to contribute to cutaneous and other inflammatory atopic disease. Objectives, To gain a better understanding of the mechanisms underlying such predisposition in order to understand different disease phenotypes and possibly identify potential treatment targets. Methods, We studied 33 individuals with atopic eczema and used interleukin-4 immunospot and human leucocyte antigen class II tetrameric complexes to investigate the peripheral blood allergen-specific CD4+ T-cell responses. Results, Filaggrin null mutations associated with significantly (P < 0·05) higher frequencies of allergen-specific CD4+ T-helper 2 cell responses. Conclusions, These data would support a model where barrier dysfunction possibly promotes greater allergen penetration and delivery to drive allergen-specific CD4+ T cells. This could further contribute to respiratory and cutaneous inflammatory disease. [source] | ||||||||||