Structural basis for differential recognition of brassinolide by its receptors

Brassinosteroids, a group of plant steroid hormones, regulate many aspects of plant growth and development. We and other have previously solved the crystal structures of BRI1(LRR) in complex with brassinolide, the most active brassinosteroid identified thus far. Although these studies provide a structural basis for the recognition of brassinolide by its receptor BRI1, it still remains poorly understood how the hormone differentiates among its conserved receptors. Here we present the crystal structure of the BRI1 homolog BRL1 in complex with brassinolide. The structure shows that subtle differences around the brassinolide binding site can generate a striking effect on its recognition by the BRI1 family of receptors. Structural comparison of BRL1 and BRI1 in their brassinolide-bound forms reveals the molecular basis for differential binding of brassinolide to its different receptors, which can be used for more efficient design of plant growth regulators for agricultural practice. On the basis of our structural studies and others' data, we also suggest possible mechanisms for the activation of BRI1 family receptors.

Inhibitory effect and kinetic analysis of sodium quercetin-7,4'-disulphate on recombinant human protein kinase CK2 holoenzyme / 药学学报

<p><b>AIM</b>To study the direct effect and kinetics of sodium quercetin-7,4'-disulphate (SQDS) on recombinant human protein kinase CK2 holoenzyme.</p><p><b>METHODS</b>The recombinant human CK2 holoenzyme activity was assayed by detecting incorporation of 32P of [gamma-32P] ATP into the substrate in various conditions.</p><p><b>RESULTS</b>The recombinant human CK2 was a second messenger (Ca2+, cAMP and cGMP) independent protein kinase. The characterization and function of the reconstituted holoenzyme were consistent with those of native CK2. SQDS was shown to strongly inhibit the holoenzyme activity of recombinant human protein kinase CK2 with an IC50 of 4.4 mumol.L-1, which was more effective than DRB and A3, known CK2 special inhibitors. Kinetic studies of SQDS on recombinant human CK2 showed: the inhibition was competitive with ATP and noncompetitive with casein.</p><p><b>CONCLUSION</b>SQDS is a potent inhibitor of protein kinase CK2. This study provide experimental basis for the development of more effective inhibitors of CK2 and for clinical application of SQDS in the future.</p>

Separation and identification of quercetin,genistein and their sulphate derivatives with micellar paper chromatography / 中国药学杂志

OBJECTIVE：To investigate the use of micellar paper chromatography on the isolation and identification of flavonoids and their soluble derivatives.METHOD:Quercetin,Genistein and their sulphate derivatives were separated and identified by SDS solution above critical micelle concentration (CMC) on paper chromatography.The concentration of SDS,ratio of organic modifier and their concentration,fluorescence were investigated.RESULTS:The best concentration of SDS micelle was 0.01～0.02mol*L-1,and the spot effects of micellar chromatography could be improved by adding 2%～4% isopropanol (or n-amyl alcohol)into the mobile phase.CONCLUSION:The simple,rapid,accurate and qualitative method could be used to analyze and isolate flavonoids and their soluble derivatives.

Preparation of quercetin-arginine complex / 中草药

Object To prepare the water soluble quercetin arginine complex (QAC) and widen the administration path of quercetin (QUE). Methods Definite QUE and L arginine were refluxed in alcohol to prepare QAC. The QAC structure was identified by micellar paper chromatography, UV spectrometry, IR spectrometry, and X ray diffraction. Results QAC was prepared from QUE and L arginine in molar ratio 1∶1. The inhibitory activity of QAC that existed stably in room temperature on cancer cell growth was as strong as that of QUE, and the solubility of QAC in water was remarkably enhanced. Conclusion The above preparation method is simple and available, and it is suitable to improve the bioavailability.