Actin-, myosin- and ubiquitin-dependent endocytosis

Endocytosis is a general term that is used to describe the internalization of external and plasma membrane molecules into the cell interior. In fact, several different mechanisms exist for the internalization step of this process. In this review we emphasize the work on the actin-dependent pathways, in particular in the yeastSaccharomyces cerevisiae, because several components of the molecular machinery are identified. In this yeast, the analysis of endocytosis in various mutants reveals a requirement for actin, calmodulin, a type I myosin, as well as a number of other proteins that affect actin dynamics. Some of these proteins have homology to proteins in animal cells that are believed to be involved in endocytosis. In addition, the demonstration that ubiquitination of some cell surface molecules is required for their efficient internalization is described. We compare the actin, myosin and ubiquitin requirements for endocytosis with recent results found studying these processes usingDictyostelium discoideum and animal cells.     

具有嗜杀质粒(killer plasmid)酵母菌嗜杀特性的初步研究

以K_2型嗜杀酵母为材料在改进Russell(1986)的嗜杀活性检测方法基础上,建立了双层平板单菌落检测法。此法可直接用于嗜杀酵母的筛选,嗜杀质粒的检测,并能在诱变后的平板上检出有嗜杀活性的营养缺陷型菌株MK_2-3:K~+,len。对K_2嗜杀特性初步研究表明,K_2型嗜杀酵母能杀死酿酒酵母(Saccha-romyces cerevisiae),但对所测汉逊酵母(Hansenula spp.)无作用。嗜杀毒素产生的最适pH和温度分别为pH4.5—5.5和20—25℃,酵母菌的对数生长期嗜杀毒素达到高峰。用紫外线(UV)、溴化乙锭(EB)、亚硝基胍(NTG)和甲基磺酸乙酯(EMS)进行消除K因子实验,表明亚硝基胍和紫外线对K因子具有一定消除率,而溴化乙锭和甲基磺酸乙酯未发现消除作用。     

An integrative model and analysis of cell cycle in fission yeast

Cell cycle is a programmed process, during which a cell proliferates to two daughter cells. The eukaryotic or-ganisms share the same characters, such as four cycle phases G1, S, G2 and M, the evolutionally conserved cell cycle proteins and its dependent kinases, and the check-points mechanism[1,2]. Due to the different functions and the complicated interactions of these proteins involved in cell cycle, it is very difficult to understand the regulatory mechanism of cell cycle in a whole sense …     

羧基在酵母菌生物吸附铅时的作用

用不同方法研究了酵母菌吸附重金属的机理.电位滴定法的结果说明生物材料含有0.5 mmol/g的酸性基团;酯化后的酵母菌对重金属的吸附量显著下降.对酯化前后的生物材料的红外光谱进行了比较,1 744 cm-1的吸收峰强度的增加证明酵母菌发生了酯化过程.羧基在酵母菌结合铅时起重要作用.     

紫外分光光度法测定啤酒酵母水溶性多糖的含量

采用紫外分光光度法对啤酒酵母中水溶性多糖的含量进行测定,发现啤酒酵母水溶性多糖在波长489nm处有最大吸收峰。葡萄糖浓度在1.55~13.286μg.mL-1(r=0.9989)范围内、线性关系良好,平均回收率在6.1%,RSD为2.3%。     

Interaction between PⅡ and NifA in Azospirillum brasilense Sp7

The interaction between PⅡ and NifA in A.brasilense Sp7 was investigated by using the yeast two-hybrid system.Our experimental results showed that PⅡ directly interacted with the entire NifA protein and its N-terminal domain,but did not interact with the central domin and the C-terminal domain of NifA.No interaction happened if glnB coding for PⅡ was frame-shift mutated.Pz,a homolog of PⅡ,had no interation with NifA.     

Fatty acid metabolism in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Peroxisomes are essential subcellular organelles involved in a variety of metabolic processes. Their importance is underlined by the identification of a large group of inherited diseases in humans in which one or more of the peroxisomal functions are impaired. The yeast Saccharomyces cerevisiae has been used as a model organism to study the functions of peroxisomes. Efficient oxidation of fatty acids does not only require the participation of peroxisomal enzymes but also the active involvement of other gene products. One group of important gene products in this respect includes peroxisomal membrane proteins involved in metabolite transport. This overview discusses the various aspects of fatty acid -oxidation in S. cerevisiae. Addressed are the various enzymes and their particular functions as well as the various transport mechanisms to take up fatty acids into peroxisomes or to export the -oxidation products out of the peroxisome to mitochondria for full oxidation to CO₂ and H₂O.Received 19 February 2003; received after revision 27 March 2003; accepted 27 March 2003     

硒酵母制备中添加不同硒化物对酵母中硒含量的影响

进行了在麦芽汁培养液中添加亚硒酸钙、亚硒酸钠、二氧化硒等多种硒化合物制备硒酵母的研究．结果表明,酵母同化各种无机硒化物为有机硒的利用度不同,其中亚硒酸钙作为硒源具有毒性小、利用度高的特点．     

啤酒酵母胞壁多糖提取工艺的研究

提出了一个从啤酒厂主要副产物－废酵母泥中制备胞壁多糖的新工艺。该工艺主要包括自，机械破碎，碱溶，中和，沉淀等工序，碱溶工序的最佳工艺条件为：按５：１（碱液体积ＭＬ：酵终胞壁湿重ｇ）比例加入２％的ＫＯＨ溶液，煮沸浸提１．５ｈ。在实验室规模下，在各工艺参数优化时，胞壁多糖得率为１０％，相对纯度达８３％，层析表明，组成胞壁多糖基本单位为甘露糖和葡萄糖。