高等植物叶片中的硝酸还原酶活性稳定因子

从小麦、油菜、浮萍、番茄、烟草的叶片中分离得到NR-SF。不同植物材料中NR及NR-SF能起交叉反应;不同NR-SF影响NR酶动力学性质相同;不同NR-SF的凝胶电泳谱带显示蛋白和糖蛋白性质。NR-SF广泛存在于植物细胞中。     

The nucleotide sequence of tobacco rattle virus RNA-2 (CAM strain).

The nucleotide sequence of the smaller genomic strand (RNA-2) of the bipartite tobacco rattle virus (CAM strain) has been determined. RNA-2 is capped at the 5' terminus and contains 1799 nucleotide residues. There is a single 223 codon long open reading frame extending from nucleotide 574 to 1242 which designates a protein of Mr 23,654. The derived amino acid composition, in percent, matches that previously determined for the virus capsid protein. The long open reading frame is flanked by 5' and 3' untranslated regions of 573 and 554 nucleotides, respectively. The 5' leader sequence contains two different sets of direct repeats, one of 119 nucleotides and the other of 76. It also contains 13 apparently unused AUG codons, four of which lie in the same frame as the capsid protein cistron. The 3' terminal sequence of RNA-2 is identical to that of the larger genomic strand (RNA-1) for 459 nucleotides.     

On the mechanism of activation of the ATP X Mg(II)-dependent phosphoprotein phosphatase by kinase FA

The mechanism of activation of the Mg(II) X ATP-dependent phosphatase by the kinase FA has been investigated. The inactive protein phosphatase can be represented as FC X M where FC is the inactive catalytic component and M is the heat-stable modulator protein (also known as inhibitor-2). Phosphorylation of the modulator protein is demonstrated during activation of FC X M. In addition, continuous ATP hydrolysis during the activation is observed. This suggests that a cyclic phosphorylation-dephosphorylation reaction is continuously occurring during the activation. It is proposed that phosphorylation of the modulator protein causes an isomerization in FC to generate an active phosphatase. The activated phosphatase is capable of dephosphorylating the phosphorylated modulator. Upon dephosphorylation of modulator, the active phosphatase returns to its inactive form via a slow isomerization.     

Nucleotide sequence of v-fps in the PRCII strain of avian sarcoma virus.

PRCII is an avian retrovirus whose oncogene (v-fps) induces fibrosarcomas in birds. The viral gene v-fps arose by transduction of an undetermined portion of a cellular gene known as c-fps. PRCII is weakly oncogenic when compared with Fujinami sarcoma virus, another transforming virus containing v-fps. As a first step in the elucidation of the molecular basis for the decreased virulence of PRCII, we have determined the entire nucleotide sequence of v-fps in the PRCII genome. The v-fps domain in PRCII encodes a polypeptide with a molecular weight of ca. 60,500 fused to a portion of the polyprotein encoded by the viral structural gene gag. The hybrid gag-fps polyprotein of PRCII would have a molecular weight of ca. 98,100, in accord with results of previous studies of the protein encoded by the PRCII genome. The leftward junctions between fps and gag in Fujinami sarcoma virus and PRCII are located at the same position in fps, but at different positions in gag. A sequence of 1,020 nucleotides, bounded by direct repeats of 6 nucleotides, is present in v-fps of Fujinami sarcoma virus but absent from PRCII. Our data should permit further explorations of the relationship between structure and function in the transforming protein encoded by v-fps.     

管花马兜铃化学成分的研究

从管花马兜铃中分得马兜铃酸-A,7-甲氧基马兜铃酸-A,马兜铃内酰胺-β-D-葡萄糖甙,尿囊素和Eupomatenoid-7。     

蚕豆植株中酰脲分布和叶片中酰脲水解活性

蚕豆根、茎和叶含有0.31～0.70 μmol酰脲·g~(-1)FW,并受结瘤和生长发育的影响。摘除正在生长的器官可观察到同腋位叶片酞脲含量暂时升高现象。 叶片中酰脲主要是尿囊酸。尿囊素酶和脲酶活性分别为0.30 μmol尿囊酸·g~(-1)FW·h~(-1)和0.19 μmol NH_3·g~(-1)FW·h~(-1)。尿囊酸含量和尿囊素酶活性日变化相似,只是后者峰值比前者出现早。     

Reexamination of the activation of yeast proteinase B at pH 5: loss of inhibition effect of proteinase B inhibitors

The activation of yeast proteinase B at pH 5 has been suggested to be due to the degradation of a specific inhibitor for the enzyme, IB, by proteinase A. However, we found that when pepstatin, which completely inhibits proteinase A, was included in the pH 5 activation mixture, the same time-dependent activation of proteinase B was observed. Furthermore, proteinase B preparations that were void of proteinase A activity were still activated by incubation at pH 5. We found that the activation of proteinase B at pH 5 was due primarily to the irreversible loss of inhibitory effect of IB, which can be resolved by isoelectrofocusing into four distinct bands with isoelectric points of 4.6, 6.1, 6.8 and 7.6. These four forms of IB showed varying degrees of stability at pH 5, which may explain some of the differing observations reported in the past.     

二十三种药用种子(或果实)中油的化学组成

本文报道了二十三种药用种子(或果实)的含油率和油的化学组成成分,它们分属于二十个科二十二个属中。本文所发表的大部分资料尚未见国内外文献的报道。     

Effects of vasoactive intestinal polypeptide, monoamines, prostaglandins, and 2-chloroadenosine on adenylate cyclase in rat cerebral microvessels

Abstract: Adenylate cyclase in microvessels isolated from rat cerebral cortex was stimulated by guanine nucleotides, catecholamines, prostaglandin E₁, prostaglandin E₂, and 2-chloroadenosine. Catecholamine stimulation was mediated by interaction with β-adrenergic receptors. The order of relative potency was: isoproterenol > epinephrine > norepinephrine. Activation of microvessel adenylate cyclase by prostaglandins E₁ and E₂ as well as by 2-chloroadenosine was dose related. Twenty-two peptides were tested for possible effects on the microvessel adenylate cyclase. Only vasoactive intestinal polypeptide (VIP) was stimulatory. No inhibitory action was observed. Activation by VIP required guanosine triphosphate and was dose dependent from 10 n M to μ M (ED₅₀= 0.1 μ M ). At 30°C, stimulation of adenylate cyclase by the peptide increased linearly with time for up to 15 min. The effect of VIP was not inhibited by phentolamine or propranolol, suggesting that its action was not elicited by interaction with α- or β-adrenergic receptors. Activation achieved by VIP and isoproterenol, prostaglandin E₁, or 2-chloroadenosine was the sum of the individual stimulations, suggesting that receptors for VIP were distinct from those for isoproterenol, prostaglandin E₁, and 2-chloroadenosine.     

Chemotactic activity of platelet alpha granule proteins for fibroblasts

At sites of blood vessel injury, platelets release numerous substances that may have biological activities influencing cellular responses. In this study we examined separately the chemotactic activity for fibroblasts of three highly purified proteins obtained from platelet alpha granules: platelet factor 4 (PF4), platelet-derived growth factor (PDGF), and beta-thromboglobulin (BTG). We observed that each of these proteins was strongly chemotactic for fibroblasts, with maximum chemotactic activity in each instance comparable to that observed with an optimal concentration of the control chemotactic protein, plasma fibronectin. Each protein was active at very low concentrations. The peak chemotactic activities of PF4, PDGF, and BTG occurred at 200 mg/ml, 30 ng/ml, and 6 ng/ml, respectively. Specificity of fibroblast chemotaxis to individual platelet proteins was provided by finding that anti-PF4 immunoglobulin blocked the chemotactic activity of PF4 without affecting the chemotactic activity of PDGF, while anti-PDGF immunoglobulin blocked the activity of PDGF but did not alter the capacity of PF4 to promote fibroblast chemotaxis. These results suggest that in vivo several alpha granule proteins released from platelets may affect wound healing by causing directed fibroblast migration.