A genomic perspective on membrane compartment organization

Now that whole genome sequences are available for many eukaryotic organisms from yeast to man, we can form broad hypotheses on the basis of the relative expansion of protein families. To investigate the molecular mechanisms responsible for the organization of membrane compartments, we identified members of the SNARE, coat complex, Rab and Sec1 protein families in four eukaryotic genomes. Of these families only the Rab family expanded from the unicellular yeast to the multicellular fly and worm. All families were expanded in humans, where we find 35 SNAREs, 60 Rabs and 53 coat complex subunits. In addition, we were able to resolve the SNARE class of proteins into four distinct subfamilies.     

人类乙型肝炎样病毒核心蛋白中第7位疏水性氨基酸重复肚段区域的突变可以抑制病毒核衣壳的组装

人类乙型肝炎病毒的核衣壳由核心蛋白的二聚体所组成．但是,核心蛋白亚单位与亚单位之间相互作用的机制至今尚不清楚．研究发现,在人类乙型肝炎样病毒──土拨鼠肝炎病毒（WHV）核心蛋白的氨基端,存在着4个保守的疏水氨基酸残基（氨基酸位置101～102）．它们分别是亮氨酸101,亮氨酸108,缬氨酸115和苯丙氨酸122．这4个疏水氨基酸残基以每隔6个氨基酸残基而重复出现1次．它们被称为“第7位疏水性氨基酸重复肽段（hhr）”．由于蛋白质中的疏水键往往在蛋白质的相互作用中起重要作用,因此就在培养细胞系统中研究WHV核心蛋白的hhr区域在…     

The PSI-H subunit of photosystem I is essential for state transitions in plant photosynthesis

Photosynthesis in plants involves two photosystems responsible for converting light energy into redox processes. The photosystems, PSI and PSII, operate largely in series, and therefore their excitation must be balanced in order to optimize photosynthetic performance. When plants are exposed to illumination favouring either PSII or PSI they can redistribute excitation towards the light-limited photosystem. Long-term changes in illumination lead to changes in photosystem stoichiometry. In contrast, state transition is a dynamic mechanism that enables plants to respond rapidly to changes in illumination. When PSII is favoured (state 2), the redox conditions in the thylakoids change and result in activation of a protein kinase. The kinase phosphorylates the main light-harvesting complex (LHCII) and the mobile antenna complex is detached from PSII. It has not been clear if attachment of LHCII to PSI in state 2 is important in state transitions. Here we show that in the absence of a specific PSI subunit, PSI-H, LHCII cannot transfer energy to PSI, and state transitions are impaired.     

人类乙型肝炎样病毒Pre—S1包膜蛋白的一个特定区域为乙肝病毒形成所必需

土拨鼠肝炎病毒（WHV）是一种哺乳类动物的肝炎病毒．这种病毒在结构和抗原怕与人类乙型肝炎病毒（HBV）非常相似．以往的研究报告指出,在一种称为鸭乙型肝炎病毒（DHBV）的Pre－S包膜蛋白中,含有一个特定区域．这一区域由天冬氨酸－天冬氨酸－脯氨酸－亮氨酸－亮氨酸（DDPLL）5个氨基酸残基所组成．已发现,这一区域在像DHBV这一类禽类乙肝病毒的病毒装配和分泌时所必需的（LenhoffR,SummersJ．JVirol,1994,68：4565～4571）．在WHV的Pre－S包胰蛋白中第201个氨基酸到第205个氨基酸所包含的顺序,甘氨酸－天冬氨酸－脯氨…     

Three-dimensional structure of the neuronal-Sec1-syntaxin 1a complex

Syntaxin 1a and neuronal Sec1 (nSec1) form an evolutionarily conserved heterodimer that is essential for vesicle trafficking and membrane fusion. The crystal structure of the nSec1-syntaxin 1a complex, determined at 2.6 A resolution, reveals that major conformational rearrangements occur in syntaxin relative to both the core SNARE complex and isolated syntaxin. We identify regions of the two proteins that seem to determine the binding specificity of particular Sec1 proteins for syntaxin isoforms, which is likely to be important for the fidelity of membrane trafficking. The structure also indicates mechanisms that might couple the action of upstream effector proteins to conformational changes in syntaxin 1a and nSec1 that lead to core complex formation and membrane fusion.     

Ecdysteroids in the adult male blowflyCalliphora vicina

Summary Male adult blowflies contain ecdysteroids. A considerable amount of ecdysteroid is concentrated in the testes and gives rise to a high local concentration. Analysis by high performance liquid chromatography and thin-layer chromatography indicate that ecdysterone is the most prominent ecdysteroid in male flies. The results can explain several hormone-dependant processes.