EFFECTS OF HELPER PROTEINS ENCODED BY p19 AND orf1-orf2 GENES ON Cyt1Aa PROTEIN EXPRESSION IN ACRYSTALLIFEROUS STRAIN OF BACILLUS THURINGIENSIS

A series of plasmids were constructed to examine the effects of p19 and orf1‐orf2 genes from Bacillus thuringiensis on Cyt1Aa synthesis and inclusion formation. The plasmids expressed the cyt1Aa gene along with either p19 or orf1‐orf2, or each of them coordinatively with p20 in the acrystalliferous strain of B. thuringiensis subsp. israelensis 4Q7. No effect on the expression of Cyt1Aa protein was found when P19 or Orf1‐Orf2 co‐expressed with Cyt1Aa. However, when including p20 gene, the constructs with p19 or orf1‐orf2 gene produced lower yield of Cyt1Aa proteins than without p19 or orf1‐orf2 gene. Electron microscopy observation and bioassay showed that P19 and Orf1‐Orf2 have no influence on the crystal size and toxicity of Cyt1Aa protein. It is presumed that P19 and Orf1‐Orf2 might have negative effects on Cyt1Aa synthesis in B. thuringiensis.     

上海四膜虫接合生殖期间皮层细胞骨架蛋白的研究

本文采用生化抽提,结合电泳及显微技术,对上海四膜虫（Ｔｅｔｒａｈｙｍｅｎａｓｈａｎｇｈａｉｅｎｓｉｓ）Ｓ１皮层细胞骨架（ｃｏｒｔｉｃａｌｃｙｔｏｓｋｅｌｅｔｏｎ）的蛋白组份,及其在接合生殖期间的变化进行了一系列的研究,初次探索了Ｓ１株上海四膜虫在接合生殖中皮细胞骨架的蛋白组份及含量,并分析了它们与间期,接合分开时期同类蛋白相互间的差异,发现在接合生殖时期７６－８８ｋＤ蛋白有突出的表现,而９０ｋＤ和     

Pharmacological comparison of bPTH-(1–34) and other hypotensive peptides in the dog

The purpose of the present study was to compare the potency, effectiveness and duration of action of synthetic bPTH-(1–34) with those of other known hypotensive peptides in the anesthetized dog. Of sixteen peptides tested in the present study only 8 were demonstrated to possess hypotensive activity. While bPTH-(1–34) was one of the least potent of the hypotensive peptides, it was equal to or greater than the other peptides in terms of effectiveness and duration of action. Of all the peptides studied, substance P and eledoisin were the most potent in terms of their hypotensive action. It is suggested that perhaps substance P and eledoisin might act at a different site or through different mechanisms than do vasoactive intestinal peptide (V.I.P.), corticotropin inhibiting peptide (C.I.P.), neurotensin, xenopsin, bradykinin and bPTH-(1–34).     

A1 adenosine receptors of bovine brain couple to guanine nucleotide-binding proteins Gi1, Gi2, and Go

A1 adenosine receptors and associated guanine nucleotide-binding proteins (G proteins) were purified from bovine cerebral cortex by affinity chromatography (Munshi, R., and Linden, J. (1989) J. Biol. Chem. 264, 14853-14859). In this study we have identified the pertussis toxin-sensitive G protein subunits that co-purify with A1 adenosine receptors by immunoblotting with specific antipeptide antisera. Gi alpha 1, Gi alpha 2, Go alpha, G beta 35, and G beta 36 were detected. Of the total [35S]guanosine 5'-O-(3-thio)triphosphate [( 35S]GTP gamma S) binding sites, Gi alpha 1 and Go alpha each accounted for greater than 37% whereas Gi alpha 2 comprised less than 13%. G beta 35 was found in excess over G beta 36. Low molecular mass (21-25 kDa) GTP-binding proteins were not detected. We also examined the characteristics of purified receptors and various purified bovine brain G proteins reconstituted into phospholipid vesicles. All three alpha-subunits restored GTP gamma S-sensitive high affinity binding of the agonist 125I-aminobenzyladenosine to a fraction (25%) of reconstituted receptors with a selectivity order of Gi2 greater than Go greater than or equal to Gi1 (ED50 values of G proteins measured as fold excess over the receptor concentration were 4.7 +/- 1.2, 24 +/- 5, and 34 +/- 7, respectively). Furthermore, receptors occupied with the agonist R-phenylisopropyladenosine catalytically increased the rate of binding of [35S]GTP gamma S to reconstituted G proteins by 6.5-8.5-fold. These results suggest that A1 adenosine receptors couple indiscriminately to pertussis toxin-sensitive G proteins.     

Stimulation by growth hormone of MAP kinase activity in 3T3-F442A fibroblasts.

We have previously demonstrated that growth hormone (GH) promotes an increase in tyrosine kinase activity associated with the GH receptor. To gain insight into the role of GH-dependent tyrosine kinase activity in signaling by GH, we investigated the possibility that GH might stimulate MAP kinase, a serine/threonine/tyrosine kinase thought to be a common element in tyrosine kinase-initiated response cascades. Treatment of 3T3-F442A fibroblasts with 100 ng/ml GH results in a 3-6-fold increase in the ability of cell-free extracts to phosphorylate MAP-2 and myelin basic protein. GH-stimulated kinase activity is unaffected by heparin, H7, or cAMP-dependent protein kinase inhibitor peptide, partially reduced by staurosporin and inhibited by fluoride and calcium ions, indicating that the kinase is not protein kinase C or A, casein kinase, or a calcium/calmodulin-dependent protein kinase. Based on gel permeation chromatography, the molecular mass of the GH-stimulated MAP kinase is approximately kDa. Furthermore, anti-phosphotyrosine antibodies revealed the GH-dependent appearance of two phosphotyrosine-containing proteins in cell-free lysates of GH-treated cells that co-migrate with proteins recognized by anti-MAP kinase antibodies. The GH-dependent increase in MAP kinase activity displays a biphasic time course and is dependent on the concentration of GH applied to the cells. GH-dependent MAP kinase activity, partially purified by Mono-Q chromatography, is inactivated by treatment with alkaline phosphatase. Addition of H7 to the cells prior to the addition of GH has no effect, whereas addition of H8 increases MAP kinase activity in control cells with no effect in GH-treated cells, indicating that protein kinase C is unlikely to be an intermediary in the GH-dependent stimulation of MAP kinase activity. These findings indicate that signaling by GH in 3T3-F443A cells may, at least in part, utilize a kinase cascade similar to those that have been proposed for other membrane receptors with associated tyrosine kinase activity.     

Cloning, genetic organization, and characterization of a structural gene encoding bacillopeptidase F from Bacillus subtilis

Bacillopeptidase F is an extracellular serine protease that is expressed at the beginning of the stationary phase. To study its structure, regulation of expression, and physiological roles, we have cloned and characterized the structural gene (bpf) encoding this protease from Bacillus subtilis. DNA sequence analysis suggests this protease is synthesized as a preproenzyme (Mr = 92,000). Through processing at both the NH2 and COOH termini, it is gradually converted into various forms with molecular mass ranging from 80 to 48 kDa. Shortening the 3' end of bpf demonstrates that at least 290 amino acid residues from the COOH-terminus of bacillopeptidase F are not required for either catalytic activity or secretion. Bacillopeptidase F exhibits sequence similarity with several serine proteases. Its gene is found immediately downstream from the fts operon which was mapped at 135 degrees on the B. subtilis genetic linkage map. Inactivation of the chromosomal copy of bpf shows no effect on cell growth and sporulation. A triple protease-deficient strain (WB300 with the structural genes for bacillopeptidase F and two other major proteases inactivated) was constructed to serve as a better expression host for the production and secretion of foreign proteins.     

Inhibition of lipogenesis and induction of apoptosis by valproic acid in prostate cancer cells via the C/EBPα/SREBP-1 pathway

Lipid metabolism reprogramming is now accepted as a new hallmark of cancer.Hence,target-ing the lipogenesis pathway may be a potential avenue for cancer treatme...     

土壤干旱胁迫对紫叶矮樱叶片呈色的影响

以盆栽3 a紫叶矮樱叶片为试材,采用称重控水法,设对照(土壤含水量18.11%)、轻度干旱(土壤含水量14.72%)、中度干旱(土壤含水量11.32%)和重度干旱(土壤含水量7.92%)4个处理组,研究不同土壤干旱条件下紫叶矮樱叶片呈色色素含量、可溶性糖含量、PAL酶活性的变化规律及其对叶片呈色的影响.结果表明:轻度干旱,随胁迫时间的延长叶片中花青苷、类黄酮、叶绿素、可溶性糖含量、PAL酶活性和a*增加, L*和b*降低;中度和重度干旱,随胁迫时间的延长花青苷、类黄酮、叶绿素、类胡萝卜素、可溶性糖含量、PAL酶活性和a*先增加再降低,L*和b*先减小再增大.短时间的干旱能够提高紫叶矮樱的叶片色泽,中度干旱15 d或重度干旱12 d,是紫叶矮樱叶色发生明显转变的关键时期;花青苷含量的变化是影响紫叶矮樱叶色变化的主要原因.     

西南喀斯特木本植物区系成分的纬度变异格局

本研究选取3个极具代表性的喀斯特原生植被区域,即北热带的广西弄岗自然保护区、南亚热带的广西龙虎山自然保护区和中亚热带的贵州茂兰自然保护区为研究对象,通过野外实地调查及查阅文献,整理出3个区域的木本植物名录,比较分析木本植物种类组成和区系成分的纬度变异格局。结果显示,弄岗、龙虎山和茂兰3个不同气候区域内的木本植物分别有104科425属936种、99科363属636种和100科352属995种。木本植物区系均以热带亚热带成分为主,其优势科热带性质随纬度升高逐步降低。热带区系成分与温带区系成分的比值(R/T)反映出,弄岗和龙虎山自然保护区的木本植物区系属的热带性质明显,而茂兰自然保护区植物属的热带性质较弱,温带性质属的比重随纬度升高而增加。科、属、种相似性系数表明,弄岗和龙虎山间的木本植物亲缘关系较密切,弄岗和茂兰间次之,而龙虎山和茂兰间亲缘关系较远。