Properties and possible functions of the adenylate cyclase in plasma membranes of Saccharomyces cerevisiae

We have examined the possible role of adenosine 3',5'-phosphate (cAMP) in functions associated with the plasma membranes of Saccharomyces cerevisiae. Purified membranes from this source contained an adenylate cyclase which was insensitive to activation by fluoride or guanine nucleotides, only weakly responsive to changes of carbon source in the growth medium, and strongly stimulated by vanadate. They also contained at least two classes of receptor proteins for guanine nucleotides (as measured by binding of labeled 5'-guanylyl methylene diphosphate) with apparent dissociation constants equal to 1.0 x 10(-7) and 3 x 10(-6) M, a protein kinase capable of phosphorylating added histones, the activity of which was stimulated by cAMP, and cAMP receptors that may function as regulatory subunits for this kinase. Membrane proteins were also susceptible to phosphorylation by endogenous kinase(s), with polypeptides of apparent molecular weights equal to 160 x 10(3), 135 x 10(3), 114 x 10(3), and 58 x 10(3) as the major targets. Of these, the 114,000-molecular-weight polypeptide was probably identical to the proton-translocating ATPase of the membranes. However, the cAMP-dependent protein kinase did not appear to be involved in these reactions. Intact (rho+ or rho0) cells responded to dissipation of the proton electrochemical gradient across their plasma membranes by rapid and transient changes in their intracellular level of cAMP, as suggested earlier (J. M. Trevillyan and M. L. Pall, J. Bacteriol., 138:397-403, 1979). Thus, although yeast plasma membranes contain all the essential components of a stimulus-responsive adenylate cyclase system, the precise nature of the coupling device and the targets involved remain to be established.     

基于最大熵生态位模型的中华穿山甲潜在适宜生境预测

中华穿山甲（Manis pentadactyla）属于全球极度濒危物种,也是我国一级保护动物。对中华穿山甲的非法捕杀曾导致其种群数量锐减。但是,近年来相关研究报道较少,穿山甲分布状况不明,极大地制约了对该物种的有效保护。搜集了近年来国内中华穿山甲的救护记录和救护新闻,甄别出67个记录分布点,利用最大熵模型软件（MaxEnt）进行因子筛选,结果表明最冷季度降水量、人口密度、年降水量、坡度、坡向、海拔等6个环境变量是与中华穿山甲分布显著相关的影响因子。基于6个主导环境变量构建的MaxEnt模型AUC平均值为0.961±0.014,预测结果达到极好标准。刀切法（Jackknife）表明,其中最冷季度降水量、年降水量、人口密度和海拔是影响中华穿山甲分布的主要因素。中华穿山甲适宜生境（出现概率大于0.498）具有以下特点：最冷季度降水量141.22-439.46 mm,年降水量1471.67-2386.56 mm,人口密度≥390人/km²,海拔<316.98 m。该模型预测中华穿山甲在我国的潜在分布适宜区主要位于我国长江以南地区,总面积约为74.27×10⁴ km²,占国土面积的7.73%,主要集中在江西、广东、湖南和广西省,面积分别占该区域的97.58%,89.65%,76.90%和73.08%;其次是浙江、福建、台湾和安徽省。湖北、江苏、四川、云南、贵州等省份也有中华穿山甲的零星分布。湖北东南部、江苏南部、浙江西南部和福建西北部等与江西接壤的区域也是中华穿山甲的重要潜在分布适宜区。明确中华穿山甲的潜在分布适宜区,可为该物种的种群保护和栖息地管理提供科技支撑。     

sickle, a novel Drosophila death gene in the reaper/hid/grim region, encodes an IAP-inhibitory protein

Inhibitors of apoptosis proteins (IAPs) interact with caspases and inhibit their protease activity, whereas the IAP-inhibitory proteins Smac/DIABLO in mammals and Reaper, Hid, and Grim in flies relieve IAP-mediated inhibition to induce cell death. Here we describe the functional characterization of the novel Drosophila cell death protein Sickle (Skl), which binds to IAPs and neutralizes their apoptotic inhibitory activity. Skl exhibits no sequence homology to Reaper, Hid, Grim, or Smac/DIABLO, except within the 4 residue N-terminal IAP binding motif. Skl interacts with Drosophila and mammalian IAPs and can promote caspase activation in the presence of IAPs. Consistent with these findings, expression of Skl in Drosophila and mammalian cell lines or in Drosophila embryos induces apoptosis. Skl can also synergize with Grim to induce cell death in the Drosophila eye imaginal disc. Based on biochemical and structural data, the N terminus of Skl, like that of the mammalian Smac/DIABLO, is absolutely required for its apoptotic and caspase-promoting activities and its ability to interact with IAPs. These findings point to conservation in the structure and function of the IAP-inhibitory proteins across species and suggest the existence of other family members.     

Detection of protease-resistant cervid prion protein in water from a CWD-endemic area

Chronic wasting disease (CWD) is the only known transmissible spongiform encephalopathy affecting free-ranging wildlife. Although the exact mode of natural transmission remains unknown, substantial evidence suggests that prions can persist in the environment, implicating components thereof as potential prion reservoirs and transmission vehicles.^1–4 CWD-positive animals may contribute to environmental prion load via decomposing carcasses and biological materials including saliva, blood, urine and feces.^5–7 Sensitivity limitations of conventional assays hamper evaluation of environmental prion loads in soil and water. Here we show the ability of serial protein misfolding cyclic amplification (sPMCA) to amplify a 1.3 × 10⁻⁷ dilution of CWD-infected brain homogenate spiked into water samples, equivalent to approximately 5 × 10⁷ protease resistant cervid prion protein (PrP^CWD) monomers. We also detected PrP^CWD in one of two environmental water samples from a CWD endemic area collected at a time of increased water runoff from melting winter snow pack, as well as in water samples obtained concurrently from the flocculation stage of water processing by the municipal water treatment facility. Bioassays indicated that the PrP^CWD detected was below infectious levels. These data demonstrate detection of very low levels of PrP^CWD in the environment by sPMCA and suggest persistence and accumulation of prions in the environment that may promote CWD transmission.Key words: prions, chronic wasting disease, water, environment, serial protein misfolding cyclic amplification