一种能表现水稻基因组DNA分化特征的重复DNA顺序

用ＤＮＡ 复性动力学方法克隆到一个水稻中度重复顺序。Ｓｏｕｔｈｅｒｎ 杂交、限制性内切酶分析及序列分析资料表明,该重复顺序在水稻基因组中具有串联重复和散布状态两种存在方式。以该ＤＮＡ 片段作探针,用Ｓｏｕｔｈｅｒｎ 杂交方法分析了多种野生稻种和栽培稻品种的基因组分化特征。某些限制性内切酶消化过的水稻ＤＮＡ,其图谱呈现出多达４０ 条以上的杂交带,包括强杂交带和弱杂交带两种类型。重复实验结果证明,强杂交带表现为ＢＢＣＣ染色体组型特异而弱带则在栽培稻各品种间显示出丰富的多态性,表明该重复顺序片段在水稻理论研究和育种实践中可能具有重要意义     

Localization of a New Type of X-Linked Liver Glycogenosis to the Chromosomal Region Xp22 Containing the Liver α-Subunit of Phosphorylase Kinase (PHKA2)

We describe here a new type of X-linked liver glycogen storage disease. The main symptoms include liver enlargement and growth retardation. The clinical and biochemical abnormalities of this glycogenosis are similar to those of classical X-linked liver glycogenosis due to phosphorylase kinase deficiency (XLG). However, in contrast to patients with XLG, the patients described here have no reduced phosphorylase kinase activity in erythrocytes and leukocytes, and no enzyme deficiency could be found. Linkage analysis of four families with this X-linked type of liver glycogenosis assigned the disease gene to Xp22. Lod scores obtained with the markers DXS987, DXS207, and DXS999 were 3.97, 2.71, and 2.40, respectively, all at 0% recombination. Multipoint linkage analysis localized the disease gene between DXS143 and DXS989 with a maximum lod score of 4.70 at θ = 0, relative to DXS987. As both the classical XLG gene and the liver α-subunit of PHK (PHKA2) are also located in Xp22, this variant type of XLG may be allelic to classical XLG, and both diseases may be caused by mutations in PHKA2. Therefore, we propose to classify XLG as XLG type I (the classical type of XLG) and XLG type II (the variant type of XLG).     

Regulation of Saccharomyces cerevisiae CDC7 function during the cell cycle.

The yeast Cdc7 function is required for the G1/S transition and is dependent on passage through START, a point controlled by the Cdc28/cdc2/p34 protein kinase. CDC7 encodes a protein kinase activity, and we now show that this kinase activity varies in the cell cycle but that protein levels appear to remain constant. We present several lines of evidence that periodic activation of CDC7 kinase is at least in part through phosphorylation. First, the kinase activity of the Cdc7 protein is destroyed by dephosphorylation of the protein in vitro with phosphatase. Second, Cdc7 protein is hypophosphorylated and inactive as a kinase in extracts of cells arrested at START but becomes active and maximally phosphorylated subsequent to passage through START. The phosphorylation pattern of Cdc7 protein is complex. Phosphopeptide mapping reveals four phosphopeptides in Cdc7 prepared from asynchronous yeast cells. Both autophosphorylation and phosphorylation in trans appear to contribute to this pattern. Autophosphorylation is shown to occur by using a thermolabile Cdc7 protein. A protein in yeast extracts can phosphorylate and activate Cdc7 protein made in Escherichia coli, and phosphorylation is thermolabile in cdc28 mutant extracts. Cdc7 protein carrying a serine to alanine change in the consensus recognition site for Cdc28 kinase shows an altered phosphopeptide map, suggesting that this site is important in determining the overall Cdc7 phosphorylation pattern.     

Isolation, characterization and expression analysis of a leaf-specific phosphoenolpyruvate carboxylase gene in Oryza sativa.

Suppression subtractive hybridization was carried out to enrich gene fragments over-expressed in rice leaves by subtraction to rice roots, from which two identical cDNA fragments were identified to encode putative phosphoenolpyruvate carboxylase. Then the corresponding full-length cDNA (Osppc) is isolated by RT-PCR and sequenced, which indicates an open reading frame of 2895bp is contained. Its deduced protein is encoded in 10 exons and shows high similarity to many other plant PEPCs. Comparing with maize and bacterial PEPCs, it is revealed that OSPPC shares many conserved domains and active sites that responsible for the structure, activity and regulation of this enzyme. Phylogenetic analysis demonstrates that OSPPC is grouped with C3 form PEPCs of wheat, maize and sorghum, which is consistent with the classification of rice. And a putative promoter element is predicted with DOF binding box, CAAT box and TATA box in the 5'-flanking sequence of Osppc gene. Moreover, Quantitative RT-PCR analyses are performed in hybrid rice and its parents, which show that Osppc is specifically expressed in leaf including leaf vein and sheath.     

Crystal structure of Streptomyces diastaticus No. 7 strain M1033 xylose isomerase

The crystal structures of Streptomyces diastaticus No. 7 strain M1033 xylose isomerase (SDXyI) have been analysed and refined at 0.19nm. The crystal space group is I222, with unit cell dimensions of a=9.884 ran, b=9.393nm and c=8.798nm. Based on the coordinates of the Streptomyces rubiginosus xylose isomerase (SRXyI), the initial model of SDXyl was built up by the dose packing analysing and R-factor searching and refined by PROLSQ to a final R-factor of 0.177 with the rms deviations of bond lengths and bond angles of 0.001 9nm and 2.1°, respectively. No significant global conformation change existed between SRXyI and SDXyI except the local conformation in the active site.     

小鼠外胎盘锥细胞与层粘连蛋白相互作用机制的研究

本文用LN及含其活性位点序列的合成肽段cYIGSR和RGDS对小鼠EPC细胞与LN的相互作用机制进行研究。结果表明:合成肽段cYIGSR和RGDS能促进EPC粘附并具协同效应。cYIGSR还能促进EPC扩展与次生TGCs迁移。LNA链上RGD和B_1链上YIGSR两个活性位点协同地参与了LN对EPC的粘附、扩展以及次生TGCs的迁移的促进作用。cY R合用不能完全竞争性抑制EPC与LN的结合,说明还有其他作用位点存在。     

Overexpression of the yeast MCK1 protein kinase suppresses conditional mutations in centromere-binding protein genes CBF2 and CBF5

We find that overexpression in yeast of the yeast MCK1 gene, which encodes a meiosis and centromere regulatory kinase, suppresses the temperature-sensitive phenotype of certain mutations in essential centromere binding protein genes CBF2 and CBF5. Since Mck1p is a known serine/threonine protein kinase, this suppression is postulated to be due to Mck1p-catalyzed in vivo phosphorylation of centromere binding proteins. Evidence in support of this model was provided by the finding that purified Mck1p phosphorylates in vitro the 110 kDa subunit (Cbf2p) of the multimeric centromere binding factor CBF3. This phosphorylation occurs on both serine and threonine residues in Cbf2p.     

GI双突变体GIK253RA198C的构建及其性质分析

以双引物法对葡萄糖异构酶（GI）基因进行定点突变,将突变体基因于大肠杆菌中表达,获得了GI双点突变体GIK253RA198C.研究K253R和A198C双点突变对GI的结构和性质的作用,结果表明GIK253RA198C的热稳定性明显下降,最适反应温度降低5℃.文章从结构和机制上解释了为何同是K253R突变,对SM33 GI和密苏里游动放线菌GI的热稳定性产生不同的影响,认为这是由于Lys253在两种GI结构的位置上存在微小差异,从而使引入的Arg对亚基间的相互作用产生了相反效应所引起.