毛喉萜对人胃癌细胞BGC－823中蛋白激酶C及其亚类的影响

以人胃癌细胞ＢＧＣ－８２３为模型,研究了毛喉萜（ｆｏｒｓｋｏｌｉｎ）对胃癌细胞中蛋白激酶Ｃ活性及其亚类基因表达的作用,同时也观察了毛喉萜对癌基因ｃ－ｊｕｎ及抑癌基因ｐ５３表达的影响．结果表明,２×１０~（－５）ｍｏｌ／Ｌ毛喉萜处理ＢＧＣ－８２３细胞７２ｈ,细胞质、膜和细胞核ＰＫＣ活性下降,ＰＫＣ亚类β,γ基因表达被抑制,癌基因ｃ－ｊｕｎ的表达也明显降低,而抑癌基因ｐ５３表达升高,上述变化可能是毛喉萜抑制胃癌细胞增殖等生理效应的重要分子事件。     

Transformation and pp60v-src autophosphorylation correlate with SHC-GRB2 complex formation in rat and chicken cells expressing host-range and kinase-active, transformation-defective alleles of v-src.

The biochemical properties of several pp60v-src substrates believed to participate in src-mediated transformation were examined in cells expressing a kinase-active, transformation-defective v-src allele (v-src-F172 delta/Y416F) and its parental allele, v-src-F172 delta, a host-range--dependent allele that transforms chicken cells to a fusiform morphology, but does not transform rat cells. Because pp60v-src-F172 delta is dependent on autophosphorylation for transforming ability, these alleles provide a unique opportunity to examine the role of pp60v-src autophosphorylation in regulating substrate interactions. Increased pp125FAK tyrosine phosphorylation and high levels of pp60v-src-associated phosphotidylinositol-3' kinase activity were detected specifically in chicken cells exhibiting round, refractile transformation but not in cells transformed to a fusiform morphology. Increased pp125FAK kinase activity, but not increased pp125FAK tyrosine-phosphorylation correlated with pp60v-src autophosphorylation and increased anchorage-independent growth. Thus, pp125FAK and PI3'K may participate in morphological transformation by v-src. Furthermore, association of phosphorylated SHC with the adapter GRB2 correlated with increased anchorage-independent growth (and autophosphorylation) in both rat and chicken cells independent of the morphological phenotype induced. Therefore, host-range dependence for transformation may be regulated through association of SHC with GRB2, thus implicating SHC as a crucial substrate for src-dependent transformation.     

Activation of MEK family kinases requires phosphorylation of two conserved Ser/Thr residues.

MEK is a family of dual specific protein kinases which activate the extracellular signal-regulated kinases by phosphorylation of threonine and tyrosine residues. MEK itself is activated via serine phosphorylation by upstream activator kinases, including c-raf, mos and MEK kinase. Here, we report the activation phosphorylation sites of human MEK1 and yeast STE7 kinase as determined by a combination of biochemical and genetic approaches. In human MEK1, substitution of either serine residue 218 or 222 with alanine completely abolished its activation by epidermal growth factor-stimulated Swiss 3T3 cell lysates or immunoprecipitated c-raf, suggesting that both serine residues are required for MEK1 activation. Phosphopeptide analysis demonstrated that serine residues 218 and 222 of human MEK1 are the primary sites for phosphorylation by c-raf. These two serine residues are highly conserved in all members of the MEK family, including the yeast STE7 gene product, a MEK homolog in the yeast mating pheromone response pathway. Mutation of the corresponding residues in STE7 completely abolished the biological functions of this gene. These data demonstrate that MEK is activated by phosphorylation of two adjacent serine/threonine residues and this activation mechanism is conserved in the MEK family kinases.     

Vibrational analysis of nucleic acids. I. The phosphodiester group in dimethyl phosphate model compounds: (CH3O)2PO2-, (CD3O)2PO2-, and (13CH3O)2PO2-.

Normal coordinate analyses and vibrational assignments are presented for the dimethyl phosphate anion [(CH3O)2PO2-] and its deuteriomethyl [(CD3O)2PO2-] and carbon-13 [(13CH3O)2PO2-] derivatives in the gauche-gauche conformation. The dimethyl phosphate anion, which is the simplest model for the nucleic acid phosphodiester moiety, exhibits many of the spectral complexities of DNA and RNA and has previously resisted a complete and consistent vibrational analysis. In the present study we make use of new experimental data on the dimethyl phosphate isotopomers, including Raman depolarization measurements, to develop a consistent valence force field for normal modes of the C--O--P--O--C phosphodiester network and its hydrogenic substituents, as well as for stretching and bending modes of the O--P--O network of the anionic phosphodioxy group (PO2-). The force field established for dimethyl phosphate incorporates one significant nonbonded force constant, introduced from ab initio calculations, to account for interaction between the two ester C--O bonds. This study resolves previous problematic assignments for conformation-sensitive symmetric (in-phase) and asymmetric (out-of-phase) skeletal stretching modes of the ester linkages and demonstrates substantial anharmonicity in the hydrogen-stretching vibrations of the methyl substituents. New assignments are proposed for Raman bands of the phosphodioxy group, which may serve as potential indicators of structure and interaction of the DNA phosphates.     

黑曲霉突变株葡萄糖淀粉酶的化学组成及其光谱学性质

黑曲霉突变株葡萄糖淀粉酶中一型GAI舍糖量为17.6%。氨基酸分析表明,天门冬氨酸和谷氨酸(包括酰胺)占20.3%,苏氨酸和丝氨酸占25.1%,三种碱性氨基酸占6%。紫外光谱在278nm和250nm处分别有最大和最小吸收;其荧光光谱的最大激发波长和发射波长分别为284nm与342nm;远紫外CD谱表现为一双负峰;在溶液中的构象是α-螺旋10.6%,β折叠16.3%和无规卷曲73.1%。     

污染预测的非线性参数模型

本文探索了Cr~（3 ）,Cr~（6 ）溶液浓度与绿豆幼苗根过氧化物酶活性之间的相关关系,建立了线性与非线性的数学模型,经相关指数,剩余标准差检验,找出了拟合度比较高的非线性参数模型．本文的结果为利用过氧化物酶活性增长率作为水环境受重金属污染的生物监测指标提供了理论依据．     

农田林网化地区近地面层廓线特征研究

大面积林网化地区近地面层大气的系留气球观测发现,近地面层大气的风、温、湿分为两层,即下边界层和扰动边界层,其厚度和廓线分布与理查逊数有关,在中性天气条件下均满足对数分布规律,边界层（特别是扰动边界层）内的摩擦速度Ｕ．＂与旷野对比点的摩擦速度Ｕ０增大１个数量级,而粗糙度Ｚ＂０增大２个数量级,甚至更大。     

零下低温对杂交杨树皮层膜脂组成的影响

以不耐寒的美洲黑杨（Ｐｏｐｕｌｕｓｄｅｌｔｏｉｄｅｓｃｖ．“Ｌｕｘ”Ｉ－６９／５５,父本）和耐寒性较强的欧美杨（Ｐ．ｅｕｒａｍｅｒｉｃａｎａｃｌｃｖ．Ｉ－４５／５１,母本）的４个杂交Ｆ＿１代无性系（９５杨、５５９杨、６００杨和１３８１杨）为材料,分析了零下低温寒潮前后枝条皮层的脂质组成。结果表明,寒潮影响下,皮层中磷脂含量增加而组成基本不变,膜脂脂肪酸组成的变化规律是：寒潮前脂肪酸不饱和指数（ＩＵＦＡ）值大的无性系,寒潮前后的ＩＵＦＡ值变化量小;寒潮前ＩＵＦＡ值较小的无性系,寒潮前后ＩＵＦＡ值变化量较大。本文借用力学概念,提出相对抗性概念,给出杨树无性系的相对抗性序列。序列表明Ｆ＿１代无性系的耐寒性已较不耐寒的父本提高,这与田间观察基本一致。     

Direct interaction of v-Src with the focal adhesion kinase mediated by the Src SH2 domain.

The recently described focal adhesion kinase (FAK) has been implicated in signal transduction pathways initiated by cell adhesion receptor integrins and by neuropeptide growth factors. To examine the mechanisms by which FAK relays signals from the membrane to the cell interior, we carried out a series of experiments to detect potential FAK interactions with proteins containing Src homology 2 (SH2) domains that are important intracellular signaling molecules. Using v-Src-transformed NIH3T3 cells, we showed that FAK was present in the immune-complex precipitated by anti-Src antibody, suggesting potential interaction of FAK with v-Src in vivo. We also showed potentially direct interaction of FAK with v-Src in vivo using the yeast two-hybrid system. Using recombinant FAK expressed in insect cells and bacterial fusion proteins containing Src SH2 domains, we showed direct binding of FAK to the Src SH2 domain but not to the SH3 domain in vitro. A kinase-defective mutant of FAK, which is not autophosphorylated, did not interact with the Src SH2 domain under the same conditions, suggesting the involvement of the FAK autophosphorylation sites. Treatment of FAK with a protein-tyrosine phosphatase decreased its binding to the Src SH2 domain, whereas autophosphorylation in vitro increased its binding. These results confirm the importance of FAK autophosphorylation sites in its interaction with SH2 domain-containing proteins. Taken together, these results suggest that FAK may mediate signal transduction events initiated on the cell surface by kinase activation and autophosphorylation that result in its binding to other key intracellular signaling molecules.