Posttranslational N-myristoylation of BID as a molecular switch for targeting mitochondria and apoptosis

Many apoptotic molecules relocate subcellularly in cells undergoing apoptosis. The pro-apoptotic protein BID underwent posttranslational (rather than classic cotranslational) N-myristoylation when cleavage by caspase 8 caused exposure of a glycine residue. N-myristoylation enabled the targeting of a complex of p7 and myristoylated p15 fragments of BID to artificial membranes bearing the lipid composition of mitochondria, as well as to intact mitochondria. This post-proteolytic N-myristoylation serves as an activating switch, enhancing BID-induced release of cytochrome c and cell death.     

细菌菌壳作为免疫佐剂的研究进展

细菌菌壳(Bacterial ghosts,BGs)是一种不含细胞质和核酸成分的细菌空壳。近年来,研究证实BGs表面保留了大量完整的天然免疫模式识别受体的激动剂,可作为免疫佐剂诱导机体免疫或非免疫细胞分泌细胞因子,进而激活适应性免疫应答。除此之外,BGs还可装配蛋白和核酸以提高外源抗原的免疫原性。主要介绍了BGs制备技术、佐剂效应机制以及应用潜能的最新研究进展。     

An age-induced switch to a hyper-recombinational state

There is a strong correlation between age and cancer, but the mechanism by which this phenomenon occurs is unclear. We chose Saccharomyces cerevisiae to examine one of the hallmarks of cancer--genomic instability--as a function of cellular age. As diploid yeast mother cells aged, an approximately 100-fold increase in loss of heterozygosity (LOH) occurred. Extending life-span altered neither the onset nor the frequency of age-induced LOH; the switch to hyper-LOH appears to be on its own clock. In young cells, LOH occurs by reciprocal recombination, whereas LOH in old cells was nonreciprocal, occurring predominantly in the old mother's progeny. Thus, nuclear genomes may be inherently unstable with age.     

Structural basis of a phototropin light switch

Phototropins are light-activated kinases important for plant responses to blue light. Light initiates signaling in these proteins by generating a covalent protein-flavin mononucleotide (FMN) adduct within sensory Per-ARNT-Sim (PAS) domains. We characterized the light-dependent changes of a phototropin PAS domain by solution nuclear magnetic resonance spectroscopy and found that an alpha helix located outside the canonical domain plays a key role in this activation process. Although this helix associates with the PAS core in the dark, photoinduced changes in the domain structure disrupt this interaction. We propose that this mechanism couples light-dependent bond formation to kinase activation and identifies a signaling pathway conserved among PAS domains.     

Oases of the Baja California peninsula as sacred spaces of agrobiodiversity persistence

Oases have served as sacred landscapes and sources of ritual plants in arid regions of the Old and New Worlds. We evaluate the Jesuit mission oases of the Baja California peninsula (Mexico) for their role in agrobiodiversity persistence, and extend theories of sacred landscapes and biodiversity conservation to agricultural species and practices. Jesuit missionaries on the peninsula (1697–1768) introduced a suite of crops species and agricultural and water management systems that persist in the oases and have become an integral part of the cultural and religious identity of the peninsula. The sacred landscapes of the oases are defined by elements of the Jesuit mission systems, such as water capture systems and irrigation canals, stone field borders and terraces, field gardens or huertas, groves of olive trees and date palms, and multi-tiered agroecosystems. Sacred practices—including pilgrimages, religious rites, and Catholic-based community celebrations—depend on the integrated “landscapes” of the oases and on the ritual use of wild and cultivated oasis plant species. We propose that some, though not all, of the peninsula oases may be considered as sacred landscapes responsible for maintaining heritage crop species, biodiversity, and traditional farming and foodways practices.     

Domain movement in gelsolin: a calcium-activated switch

The actin-binding protein gelsolin is involved in remodeling the actin cytoskeleton during growth-factor signaling, apoptosis, cytokinesis, and cell movement. Calcium-activated gelsolin severs and caps actin filaments. The 3.4 angstrom x-ray structure of the carboxyl-terminal half of gelsolin (G4-G6) in complex with actin reveals the basis for gelsolin activation. Calcium binding induces a conformational rearrangement in which domain G6 is flipped over and translated by about 40 angstroms relative to G4 and G5. The structural reorganization tears apart the continuous beta sheet core of G4 and G6. This exposes the actin-binding site on G4, enabling severing and capping of actin filaments to proceed.     

CCAAT-enhancer binding protein: a component of a differentiation switch

The CCAAT-enhancer binding protein (C/EBP) has now been found to promote the terminal differentiation of adipocytes. During the normal course of adipogenesis, C/EBP expression is restricted to a terminal phase wherein proliferative growth is arrested, and specialized cell phenotype is first manifested. A conditional form of C/EBP was developed, making it feasible to test its capacity to regulate the differentiation of cultured adipocytes. Premature expression of C/EBP in adipoblasts caused a direct cessation of mitotic growth. Moreover, when abetted by the effects of three adipogenic hormones, C/EBP promoted terminal cell differentiation. Since C/EBP is expressed in a variety of tissues, it may have a fundamental role in regulating the balance between cell growth and differentiation in higher animals.     

Bipolar spin switch

A thin ferromagnetic film can be used to polarize the spin axes of the electrons carrying an electric current in a manner loosely analogous with a light polarizer. When such a film is fabricated on a gold film, a nonequilibrium population of spin-polarized electrons is built up in the gold causing a "spin bottleneck" effect. The addition of a second ferromagnetic film results in a device whose output voltage depends on the orientation of the spins.     

Selection on heritable phenotypic plasticity in a wild bird population

Theoretical and laboratory research suggests that phenotypic plasticity can evolve under selection. However, evidence for its evolutionary potential from the wild is lacking. We present evidence from a Dutch population of great tits (Parus major) for variation in individual plasticity in the timing of reproduction, and we show that this variation is heritable. Selection favoring highly plastic individuals has intensified over a 32-year period. This temporal trend is concurrent with climate change causing a mismatch between the breeding times of the birds and their caterpillar prey. Continued selection on plasticity can act to alleviate this mismatch.     

Structure of the nucleotide activation switch in glycogen phosphorylase a

Adenosine monophosphate is required for the activation of glycogen phosphorylase b and for release of the inhibition of phosphorylase a by glucose. Two molecules of adenosine monophosphate (AMP) bind to symmetry related sites at the subunit interface of the phosphorylase dimer. Adenosine triphosphate (ATP) binds to the same site, but does not promote catalytic activity. The structure of glucose-inhibited phosphorylase a bound to AMP and also of the complex formed with glucose and ATP is described. Crystallographic refinement of these complexes reveals that structural changes are associated with AMP but not ATP binding. The origin of these effects can be traced to different effector binding modes exhibited by AMP and ATP, respectively. The conformational changes associated with AMP binding traverse multiple paths in the enzyme and link the effector and catalytic sites.     

甲胺磷降解菌的筛选

从长期使用农药的大棚菜地的土壤中分离筛选到1号、2号、4号和8号4种甲胺磷降解菌。采用气相色谱法,分别测定了它们对甲胺磷的降解能力。结果表明,2号菌有较好的降解能力,培养28 d后对甲胺磷降解可达到46.31%。