The mahogany protein is a receptor involved in suppression of obesity

Genetic studies have shown that mutations within the mahogany locus suppress the pleiotropic phenotypes, including obesity, of the agouti-lethal-yellow mutant. Here we identify the mahogany gene and its product; this study, to our knowledge, represents the first positional cloning of a suppressor gene in the mouse. Expression of the mahogany gene is broad; however, in situ hybridization analysis emphasizes the importance of its expression in the ventromedial hypothalamic nucleus, a region that is intimately involved in the regulation of body weight and feeding. We present new genetic studies that indicate that the mahogany locus does not suppress the obese phenotype of the melanocortin-4-receptor null allele or those of the monogenic obese models (Lep(db), tub and Cpe(fat)). However, mahogany can suppress diet-induced obesity, the mechanism of which is likely to have implications for therapeutic intervention in common human obesity. The amino-acid sequence of the mahogany protein suggests that it is a large, single-transmembrane-domain receptor-like molecule, with a short cytoplasmic tail containing a site that is conserved between Caenorhabditis elegans and mammals. We propose two potential, alternative modes of action for mahogany: one draws parallels with the mechanism of action of low-affinity proteoglycan receptors such as fibroblast growth factor and transforming growth factor-beta, and the other suggests that mahogany itself is a signalling receptor.     

A vertebrate actin-related protein is a component of a multisubunit complex involved in microtubule-based vesicle motility.

Actin is a cytoskeletal protein which is highly conserved across eukaryotic phyla. Actin filaments, in association with a family of myosin motor proteins, are required for cellular motile processes as diverse as vesicle transport, cell locomotion and cytokinesis. Many organisms have several closely related actin isoforms. In addition to conventional actins, yeasts contain actin-related proteins that are essential for viability. We show here that vertebrates also contain an actin-related protein (actin-RPV). Actin-RPV is a major component of the dynactin complex, an activator of dynein-driven vesicle movement, indicating that unlike conventional actins which work in conjunction with myosin motors, actin-RPV may be involved in cytoplasmic movements via a microtubule-based system.     

The CED-4-homologous protein FLASH is involved in Fas-mediated activation of caspase-8 during apoptosis

Fas is a cell-surface receptor molecule that relays apoptotic (cell death) signals into cells. When Fas is activated by binding of its ligand, the proteolytic protein caspase-8 is recruited to a signalling complex known as DISC by binding to a Fas-associated adapter protein. A large new protein, FLASH, has now been identified by cloning of its complementary DNA. This protein contains a motif with oligomerizing activity whose sequence is similar to that of the Caenorhabditis elegans protein CED-4, and another domain (DRD domain) that interacts with a death-effector domain in caspase-8 or in the adapter protein. Stimulated Fas binds FLASH, so FLASH is probably a component of the DISC signalling complex. Transient expression of FLASH activates caspase-8, whereas overexpression of a truncated form of FLASH containing only one of its DRD or CED-4-like domains does not allow activation of caspase-8 and Fas-mediated apoptosis to occur. Overexpression of full-length FLASH blocks the anti-apoptotic effect of the adenovirus protein E1B19K. FLASH is therefore necessary for the activation of caspase-8 in Fas-mediated apoptosis.     

Assembly of yeast Sec proteins involved in translocation into the endoplasmic reticulum into a membrane-bound multisubunit complex

Secretory-protein translocation into the endoplasmic reticulum (ER) is thought to be catalysed by integral membrane proteins. Genetic selections uncovered three Saccharomyces cerevisiae genes (SEC61, SEC62 and SEC63), mutations in which block import of precursor proteins into the ER lumen in vivo and in vitro. The DNA sequences of SEC62 and SEC63 predict multispanning membrane proteins, and biochemical characterization of the SEC62 protein (Sec62) confirms that it is an integral ER membrane protein. Here we show that Sec61, Sec62 and Sec63 are assembled with two additional proteins into a multisubunit membrane-associated complex. These results confirm previous predictions, based upon genetic interactions between the SEC genes, that Sec61, Sec62 and Sec63 act together to facilitate protein translocation into the ER.     

MoFLP1, encoding a novel fungal fasciclin-like protein, is involved in conidiation and pathogenicity in Magnaporthe oryzae

Fasciclin family proteins have been identified as cell adhesion molecules in various organisms. In this study, a novel Magnaporthe oryzae fasciclin-like protein encoding gene, named MoFLP1, was isolated from a subtractive suppressive cDNA library and functionally analyzed. Sequence analysis showed that the MoFLP1 gene contains an open reading frame (ORF) of 1050 nucleotides encoding 349 amino acids with a calculated molecular weight of 35.85 kDa and a pI of 7.76. The deduced MoFLP1 protein contains a 17-amino acid secretion signal sequence and an 18-amino acid sequence with the characteristics of a glycosylphosphotidylinositol (GPI) anchor additional signal at its N- and C-terminuses, respectively. Potential N-glycosylation sites and domains involving cell adhesion were also identified in MoFLP1. Sequence analysis and subcellular localization by the expression of MoFLP1-GFP fusion construct in M. oryzae indicated that the MoFLP1 protein is probably localized on the vacuole membrane. Two MoFLP1 null mutants generated by targeted gene disruption exhibited marked reduction of conidiation, conidial adhesion, appressorium turgor, and pathogenicity. Our results indicate that fasciclin proteins play important roles in fungal development and pathogenicity in M. oryzae.     

Regulated import and degradation of a cytosolic protein in the yeast vacuole.

The key regulatory enzyme in gluconeogenesis, fructose 1,6-bisphosphatase (FBPase) is subject to glucose-stimulated proteolytic degradation in Saccharomyces cerevisiae. This process involves the regulated transfer of FBPase directly from the cytosol into the vacuole or a vacuole-related organelle. Glucose may regulate the production of an FBPase receptor or import factor that is transported to the vacuole through the secretory pathway.     

The reactivity of anti-peptide antibodies is a function of the atomic mobility of sites in a protein

To study the nature of antigenic recognition, antibodies have been prepared against a set of peptide sequences representing both highly mobile and well-ordered regions of myohaemerythrin, based on X-ray crystallographic temperature factors. Anti-peptide antibodies against highly mobile regions react strongly with the native protein; anti-peptide antibodies from well-ordered regions do not. Mobility is a major factor in the recognition of the native protein by anti-peptide antibodies; this may be of general significance in protein-protein interactions.     

An eIF-4A-like protein is a suppressor of an Escherichia coli mutant defective in 50S ribosomal subunit assembly

The assembly of ribosomes in bacterial cells is a complex process that remains poorly characterized. The in vitro assembly of active ribosomal subunits from purified RNA and protein components indicates that all of the information for proper assembly resides in the primary sequences of these macromolecules. On the other hand, the in vitro requirement of unphysiological heating steps suggests that this pathway may not accurately reflect the in vivo pathway, and that other proteins may be required. One approach to identify any additional proteins is to isolate second-site revertants of mutants defective in ribosome assembly. Ribosomal protein L24 is essential in the assembly of 50S subunits. We have identified an Escherichia coli gene, srmB, that, when expressed at high copy number, can suppress the effect of a temperature-sensitive lethal mutation in L24. The SrmB amino-acid sequence has sequence identity with mouse translation initiation factor eIF-4A and with the human nuclear protein, p68. The purified SrmB protein is a nucleic acid-dependent ATPase, like eIF-4A, but can also bind RNA in the absence of ATP and other auxiliary protein factors. The RNA dependent ATPase activity of SrmB suggests that like, eIF-4A, it could be involved in specific alterations of RNA secondary structure.     

国产复合型食品甜味剂──蛋白糖中糖精钠分析与卫生学管理探讨

目的：研究添加蛋白糖的食品中含有糖精钠的原因及商品蛋白糖卫生学管理问题。方法：应用高效液相色谱法和质谱法;调查商品蛋白糖产品介绍与使用说明中填料配方与使用规则;以及商品蛋白糖国家质量和卫生学标准。结果：商品蛋白糖中含有约10％糖精钠,其产品介绍与使用说明中未标识其配方组成和含量,特别是糖精钠;目前尚无蛋白糖的国家质量和卫生学标准。结论：制造商在商品蛋白糖中添加糖精钠是造成以蛋白糖做甜味剂的食品中含量有糖精钠的原因,建议开展蛋白糖国家质量和卫生学标准研究,加强对其产品介绍与使用说明的规范化管理。     

Oligomerization study of NHR3 and NHR4 domains from ETO protein involved in t（8;21）-associated acute myeloid leukemia

Little had been known about ETO protein until t(8;21) was found in 12%-15% of acute myeloid leukemia which resulted in AML1-ETO fusion protein. ETO protein has four conserved nervy homology regions termed NHR1-4. A lot have already been known about NHR1, 2, 4:NHR1 is homologous with the Drosophila TATA-box-associated factor 110 (TAF110); NHR2 is a dimerization domain associated with mSin3A/HDAC; NHR4 is MYND class of zinc fingers associated with NCoR/SMRT/HDAC. Only the function of NHR3 remains unclear. In order to investigate whether NHR3 domain could participate in oligomerization, we cloned and purified this domain. Through gel filtration chromatography, dynamic light scattering and dissolved crystal electrophoresis, we found that NHR3 domain was a tight tetramer. Then we cloned NHR3 4 domain (i.e. NHR3 domain plus NHR4 domain), and discovered, by gel filtration chromatography and native PAGE, that NHR3 4 domaincould form dimer in solution. This was the first time to observe that NHR3 and NHR4 domains may have some contribution to the oligomerization of ETO protein, which might recruit corepressors in the form of dimer, and stabilize ETO dimerization through convergent strength of NHR2, NHR3 and NHR4 domains and then stabilize corepressors recruitment. These speculations are very worthy of further evaluation.