2’-5’ Oligoadenylate synthetase shares active site architecture with the archaeal CCA-adding enzyme

The 2'-5' oligoadenylate synthetases (OAS) are interferon-induced antiviral enzymes that recognise virally produced dsRNA and initiate an RNA destabilisation within the infected cell. We compared the structure of OAS to that of poly adenosine polymerase (PAP) and the class I CCA-adding enzyme from Archeoglobus fulgidus (AfCCA). This comparison revealed a strong structural homology between the three enzyme families. In particular, the active sites of OAS and CCA class I enzymes are highly conserved. We conducted an extensive mutagenesis of amino acid residues within the putative active site in OAS, thereby identifying enzymatically important residues and confirming the common active site architecture for OAS and the AfCCA. Our findings also have profound implications for our understanding of the evolutionary origin of the OAS enzymes and suggest that the OAS proteins diverged from a common 3'-specific ancestor at the beginning of metazoan evolution.     

Heterodimeric adenosine receptors: a device to regulate neurotransmitter release

Since 1990 it has been known that dimers are the basic functional form of nearly all G-protein-coupled receptors (GPCRs) and that homo- and heterodimerization may play a key role in correct receptor maturation and trafficking to the plasma membrane. Nevertheless, homo- and heterodimerization of GPCR has become a matter of debate especially in the search for the precise physiological meaning of this phenomenon. This article focuses on how heterodimerization of adenosine A₁ and A_2A receptors, which are coupled to apparently opposite signalling pathways, allows adenosine to exert a fine-tuning modulation of striatal glutamatergic neurotransmission, providing a switch mechanism by which low and high concentrations of adenosine inhibit and stimulate, respectively, glutamate release. Received 8 May 2006; received after revision 19 June 2006; accepted 17 July 2006     

腺苷诱导神经细胞Ca~(2+)响应的微孔板荧光检测

以钙离子荧光指示剂Fluo-3-AM作为神经细胞内Ca2+荧光探针,用微孔板荧光检测仪测量神经细胞内游离Ca2+与荧光探针Fluo-3-AM结合的荧光强度,并实时检测此荧光强度在细胞外加不同浓度腺苷诱导下的变化情况。实验发现,各种浓度的腺苷都能诱导神经细胞Ca2+浓度升高,且其影响程度随腺苷浓度的增大而增强。这一结果对探究腺苷通过作用神经系统起止痛作用的机理具有重要意义。     

L-谷氨酸-5-甲酯金属化合物的合成、表征和生物活性

在仿自然的条件下,合成了上L-谷氨酸-5-甲酯.对L-谷氨酸-5-甲酯晶体进行了X-射线单晶衍射测定.测量表明,L-谷氨酸-5-甲酯属单斜晶系,C2空间群,其中α=10.286(3)(A),b=4.6163(11)(A),c=17.111(4)(A);β=104.995(4)°.通过L-谷氨酸-5-甲酯与MgCl2·6H2O和Ca(OH)2反应,分别合成得到了相应的金属化合物.用比色法测试了L-谷氨酸-5-甲酯对三磷酸腺苷二钠分解的催化活性,结果表明:L-谷氨酸-5-甲酯合镁和L-谷氨酸-5-甲酯合钙对三磷酸腺苷二钠的分解具有较好的活性.     

不同山药种质资源的腺苷含量比较研究

目的为了解山药资源腺苷含量情况,进一步对该部分资源的腺苷含量进行分析。方法采用高效液相色谱法测定不同种质资源山药腺苷含量。结果不同种质薯蓣腺苷含量差异极显著,其中腺苷含量最高的是山东兖州的山药(0.199%);最低是河南焦作的山药(0.019%);总平均含量为0.095%。结论不同种质来源的山药腺苷含量差异较大,提示临床用药应注意不同种质来源,同时也为薯蓣的引种提供依据。     

甘薯叶片衰老的生理变化

用处于不同衰老时期的甘薯叶片为材料，研究了与衰老有关的多项生理指标的变化，比较了品种间抗衰老能力的强弱。结果指出，用能量（ＡＴＰ）耗损的观点结合其与气孔开闭运动的关系的研究，是深入认识和理解叶片衰老机制的有益途径。     

Cysteine Not Required for Catalytic Activity of Adenosine Deaminase

ＣｙｓｔｅｉｎｅＮｏｔＲｅｑｕｉｒｅｄｆｏｒＣａｔａｌｙｔｉｃＡｃｔｉｖｉｔｙｏｆＡｄｅｎｏｓｉｎｅＤｅａｍｉｎａｓｅ＊ＣｈａｎｇＺｅｎｇｙｉ（昌增益），ＤａｖｉｄＫ．Ｗｉｌｓｏｎ＋，ＲｏｄｎｅｙＥ．Ｋｅｌｅｍｓ＋，ＦｌｏｒａｎｔｅＡ．Ｑｕｉｏｃｈｏ...     

鬼桕毒自旋标记物的生物活性——对HeLa、BHK及KMB细胞的体外抑制和对cAMP-PDE的影响

用鬼桕毒自旋标记衍生物对子宫颈癌细胞(HeLa)、乳地鼠肾传代细胞(BHK)和人胚肺成纤维细胞(KMB)进行了体外抑制试验,发现鬼桕毒自旋标记衍生物在用量为0.1毫克时,对HeLa、BHK细胞有较强的抑制作用。我们还就鬼桕毒自旋标记衍生物对兔脑环腺苷酸磷酸二酯酶(cAMP-PDE)活性的抑制效果进行了观察.结果表明,对cAMP-PDE活性有较强的抑制,抑制率普遍与阳性药物-氨茶碱相近似,达30—40％。