中国人看生物技术——2003-2007研究报告

本文基于中国公众对生物技术应用态度的研究,项目从2003年开始到2007年结束,先后获得中国和丹麦政府间科技合作项目、浙江省自然科学基金、浙江省科技国际合作项目的资助.研究参照欧洲EUROBAROMETER研究范式设计问卷,采用职业分层抽样的方法,对我国代表性样本浙江四个地区的4157名公众进行了生物技术应用态度的纵向实证研究,定量分析并定性描述了我国公众对生物技术应用态度的轮廓和远景.     

Structure and assembly of the 20S proteasome

The barrel-shaped 20S proteasome is one of the two components of a larger 26S particle, the multicatalytic 2000-kDa protease complex. The proteolytic sites are located in the inner chamber of the 20S particle and are only accessible via narrow entrances. This paper reviews the current knowledge concerning proteasome formation, proteolytic activities, structural aspects and assembly. Eukaryotic proteasomes are made up by four rings each of which contains seven different subunits occurring at fixed positions. While the outer rings contain α-type subunits, the inner ones comprise β-type subunits. The current assembly model for eukaryotic 20S proteasomes is based upon the detection of 13S and 16S intermediates, respectively, in addition to previous findings with archaebacterial and eubacterial proteasome assembly. The available data suggest a cooperative assembly of the α-type and β-type subunits into half proteasome-like complexes followed by dimerization into proteasomes. During or after dimerization of half proteasomes, the β-type subunits are processed. The prosequence of the β-type subunits is essential for the assembly process and prevents protease activity of immature proteasomes.     

Bacterial nonspecific acid phosphohydrolases: physiology, evolution and use as tools in microbial biotechnology

Bacterial nonspecific acid phosphohydrolases (NSAPs) are secreted enzymes, produced as soluble periplasmic proteins or as membrane-bound lipoproteins, that are usually able to dephosphorylate a broad array of structurally unrelated substrates and exhibit optimal catalytic activity at acidic to neutral pH values. Bacterial NSAPs are monomeric or oligomeric proteins containing polypeptide components with an M _r of 25 – 30 kDa. On the basis of amino acid sequence relatedness, three different molecular families of NSAPs can be distinguished, indicated as molecular class A, B and C, respectively. Members of each class share some common biophysical and functional features, but may also exhibit functional differences. NSAPs have been detected in several microbial taxa, and enzymes of different classes can be produced by the same bacterial species. Structural and phyletic relationships exist among the various bacterial NSAPs and some other bacterial and eucaryotic phosphohydrolases. Current knowledge on bacterial NSAPs is reviewed, together with analytical tools that may be useful for their characterization. An overview is also presented concerning the use of bacterial NSAPs in biotechnology. Received 21 November 1997; received after revision 10 March 1998; accepted 10 March 1998     

Nitric oxide biosynthesis, nitric oxide synthase inhibitors and arginase competition for L-arginine utilization

Nitric oxide (NO) is a recently discovered mediator produced by mammalian cells. It plays a key role in neurotransmission, control of blood pressure, and cellular defense mechanisms. Nitric oxide synthases (NOSs) catalyze the oxidation of L-arginine to NO and L-citrulline. NOSs are unique enzymes in that they possess on the same polypeptidic chain a reductase domain and an oxygenase domain closely related to cytochrome P450s. NO and superoxide formation as well as NOS stability are finely regulated by Ca²⁺/calmodulin interactions, by the cofactor tetrahydrobiopterin, and by substrate availability. Strong interactions between the L-arginine-metabolizing enzymes are clearly demonstrated by competition between NOSs and arginases for L-arginine utilization, and by potent inhibition of arginase activity by N^ω-hydroxy-L-arginine, an intermediate in the L-arginine to NO pathway.