STRUCTURAL REQUIREMENT FOR CLUSTERS TO BE RECONSTITUTED WITH THE FeMoCo DEFICIENT MOLYBDENUM IRON PROTEIN

By incubating the reduced MoFe protein from Azotobacter vinelandii with O phenanthroline under air and chromatographying the incubated solution on Sephadex G 25 column, inactive MoFe protein could be obtained. Its acetylene reduction activity was remarkably recovered not only by incubation with the reconstituent solution composed of KMnO 4,ferric homocitrate, Na 2S and dithiothreitol,Azotobacter vinelandii with O phenanthroline under air and chromatographying the incubated solution on Sephadex G 25 column, inactive MoFe protein could be obtained. Its acetylene reduction activity was remarkably recovered not only by incubation with the reconstituent solution composed of KMnO 4,ferric homocitrate, Na 2S and dithiothreitol, with O phenanthroline under air and chromatographying the incubated solution on Sephadex G 25 column, inactive MoFe protein could be obtained. Its acetylene reduction activity was remarkably recovered not only by incubation with the reconstituent solution composed of KMnO 4,ferric homocitrate, Na 2S and dithiothreitol, but also with a mixture of 4Fe∶4S clusters and another cluster which had two structure units of 1Mo∶3Fe∶4S bridged by three -OCH 3- at the Mo atoms. Neither the reconstituent solution nor the mixture could reactivate apo MoFe proteins from the mutants deleting nifE and nifH genes and from the mutant UW 45 , which could be reactivated by the FeMoco extracted from the MoFe protein. The results indicated that the FeMoco deficient MoFe proteins from these mutants seemed to be reconstituted only by the clusters which were probably structures only similar to FeMoco. The partially metallocluster deficient MoFe protein could be reconstituted by the clusters with a certain kind of structure and composition; and was changed into different nitrogenase proteins with the ability to fix nitrogen.

Identification of an epitope of SARS-coronavirus nucleocapsid protein

The nueleocapsid (N) protein of severe acute respiratory syndrome-coronavirus (SARS-CoV) is a major virion structural protein. In this study, two epitopes (Nl and N2) of the N protein of SARS-CoV were predicted by bioinformatics analysis. After immunization with two peptides, the peptides-specific antibodies were isolated from the immunized rabbits. The further experiments demonstrated that N1 peptide-induced polyclonal antibodies had a high affinity to bind to E. coli expressed N protein of SAR,S-CoV. Furthermore, it was confirmed that Nl peptide-specific IgG antibodies were detectable in the sera of severe acute respiratory syndrome (SARS) patients. The results indicated that an epitope of the N protein has been identified and N protein specific Abs were produced by peptide immunization, which will be useful for the study of SARS-CoV.

Characterization of a S-locus-related Receptor-like Kinase Cluster in Rice Chromosome 4

We have identified 14 S _locus glycoprotein (SLG)_related protein kinase genes in a 323 kb contig of rice (Oryza sativa L.) chromosome 4 and we detected the transcription pattern of this gene cluster by reverse transcription_polymerase reaction (RT_PCR). RT_PCR results revealed that nine putative genes were transcribed in rice and these genes had the different expression patterns: two genes are expressed predominantly in reproductive tissues while the other seven genes are expressed in both reproductive and vegetative tissues. Analysis of the predicted amino acid sequences demonstrated that the extracellular receptor domains are highly homologous to SLG of Brassica, whereas the cytoplasmic kinase domains contain conserved amino acids present in serine/threonine kinases.

Impact of Borate on Structure of Antifreeze Glycoproteins

Antifreeze glycoproteins(AFGPs)facilitate the survival of various organisms in the polar region by preventing internal ice accumulation via an adsorption-inhibition mechanism.Inhibition of AFGP antifreeze activity by the borate buffers has been widely acknowledged as the direct experimental evidence supporting the hydroxyl,rather than methyl,binding mechanism.On the other hand,perturbation of borate binding on the AFGP configuration,which might have considerable influence on the binding efficiency of not only the hydroxyl but also the methyl groups,has rarely been quantitatively examined.Herein we studied,using molecular dynamics simulations,the perturbation on the configuration of a solvated AFGP8 protein induced by the binding of one single borate anion.Near the freezing point,this binding not only makes the disaccharide groups adjacent to the borate-binding disaccharide close to each other but also affects the entire AFGP8 conformation.The structural changes induced by the binding of borate on different disaccharide sidechains exhibit clear site-specificities and the effect of borate binding on the structural changes is significantly reduced at higher temperatures.Our study is valuable for further understanding the relationship between the structure and antifreeze activity of these antifreeze glycoproteins.

Analysis and Simulation of Molecular Dynamics of Lysozyme in Water Cluster System

The influence of water on protein conformation was investigated by simulating the molecular dynamics of a model protein lysozyme in different water systems.The lysozyme-water system with TIP3P water model and lysozyme-water cluster system with six-ring water model were evaluated.In addition,the radial distribution function of solvent around lysozyme was calculated.It is found that the distribution of water molecules around lysozyme is similar to that of water clusters.The analyses of dihedral angles and disulfide bonds of lysozyme show that the conformation of lysozyme is severely damaged in the lysozyme-water cluster system compared with that in the lysozyme-water system.This difference can be attributed to the formation of larger number of intermolecular hydrogen bonds between lysozyme and water cluster.It is in agreement with the analysis that water clusters can change the degree of denaturation in the process of heat denaturation of lysozyme.

Prediction of antigenic determinants of trichosanthin by molecular modeling

The antigenic determinants of trichosanthin were predicted by molecular modeling. First, the threedimensional structure model of the antigen-binding fragment of anti-trichosanthin immunoglobulin E was built on the basis of its amino-acid sequence and the known three-dimensional structure of an antibody with similar sequence. Secondly, the preferable antigen-antibody interactions were obtained based on the known three-dimensional structure of trichosanthin and of the hypervariable regions of anti-trichosanthin immunoglobulin E. Two regions in the molecular surface of trichosanthin were found to form extensive interactions with the hypervariable regions of the antibody and have been predicted to be the possible antigenic determinants: one is composed of two polypeptide segments, Ile201-Glu210 and Ile225-Asp229, which are close to each other in the three-dimensional structure; and the other is the segment Lys173-Thr178. The former region seems to be the more reasonable antigenic determinant than the latter one.

白族花草月粥

白族花草月粥章天柱花草，除供人类观赏外，还供人们食用和药用。居住在云南滇西北山区的白族群众，在长期的生活实践中，总结出一整套“花草食谱”。花草“月粥”便是其食谱中的一朵“奇葩”。所谓“月粥”，就是每月吃一种用花草配粮食熬制的粥。各月佐粥的花草原料互不...

Anti-CD69 monoclonal antibody treatment inhibits airway inflammation in a mouse model of asthma

Objective： Airway inflammation and airway hyper-responsiveness（AHR） are principle pathological manifestations of asthma. Cluster of differentiation 69（CD69） is a well-known co-stimulatory factor associated with the activation, proliferation as well as apoptosis of immune cells. This study aims to examine the effect of anti-CD69 monoclonal antibody（m Ab） on the pathophysiology of a mouse model of asthma. Methods： A murine model of ovalbumin（OVA）-induced allergic airway inflammation was used in this study. Briefly, mice were injected with 20 μg chicken OVA intraperitoneally on Days 0 and 14, followed by aerosol provocation with 1%（0.01 g/ml） OVA on Days 24, 25, and 26. Anti-CD69 m Ab or isotype Ig G was injected intraperitoneally after OVA challenge; dexamethasone（DXM） was administrated either before or after OVA challenge. AHR, mucus production, and eosinophil infiltration in the peribronchial area were examined. The levels of granulocyte-macrophage colony-stimulating factor（GM-CSF） and interleukin-5（IL-5） in bronchoalveolar lavage fluid（BALF） were also assayed as indices of airway inflammation on Day 28 following OVA injection. Results： Pretreatment with DXM together with anti-CD69 m Ab treatment after OVA provocation completely inhibited AHR, eosinophil infiltration and mucus overproduction, and significantly reduced BALF IL-5. However, treatment with DXM alone after OVA challenge only partially inhibited AHR, eosinophil infiltration and mucus overproduction, and did not diminish BALF IL-5. Treatment with either DXM or anti-CD69 m Ab did not alter the concentration of BALF GM-CSF. Conclusions： Anti-CD69 m Ab treatment inhibits established airway inflammation as effectively as DXM pretreatment. This study provides a potential alternative therapeutic opportunity for the clinical management of asthma and its exacerbation.

Cloning and characterization of the gene cluster required for beauvericin biosynthesis in Fusarium proliferatum

Beauvericin, a cyclohexadepsipeptide-possessing natural product with synergistic antifungal, insecticidal, and cytotoxic activities. We isolated and characterized the fpBeas gene cluster, devoted to beauvericin biosynthesis, from the filamentous fungus Fusarium proliferatum LF061. Targeted inactivation of the F. proliferatum genomic copy of fpBeas abolished the production of beauvericin. Comparative sequence analysis of the FpBEAS showed 74% similarity with the BbBEAS that synthesizes the cyclic trimeric ester beauvericin in Beauveria bassiana, which assembles N-methyl-dipeptidol monomer intermediates by the programmed iterative use of the nonribosomal peptide synthetase modules. Differences between the organization of the beauvericin loci in F. proliferaturm and B. bassiana revealed the mechanism for high production of beauvericin in F. proliferatum. Our work provides new insights into beauvericin biosynthesis, and may lead to beauvericin overproduction and creation of new analogs via synthetic biology approaches.