B-3 exopolysaccharide is extracted from the Antarctic psychrophilic bacterium Psychrobacter sp. B-3. We have previously shown that it activates macrophages and affects their immunoregulatory activities. To determine w...B-3 exopolysaccharide is extracted from the Antarctic psychrophilic bacterium Psychrobacter sp. B-3. We have previously shown that it activates macrophages and affects their immunoregulatory activities. To determine what genes are affected during this process, we detected the genes differentially expressed in cells of RAW264.7 macrophages treated with B-3 exopolysaccharide by transcriptomic analysis. B-3 exopolysaccharide treatment caused differential expression of 420 genes, of which 178 were up-regulated and 242 were down-regulated. These genes were shown to be involved in many aspects of cell function, mainly metabolism and immunity. Genes were enriched in multiple immune-related pathways, and the most significantly enriched genes were involved in antigen processing and presentation pathways. The pathway in which differentially expressed genes were the most significantly enriched was the metabolic pathway; specifically, the expression of many metabolic enzyme genes was altered by B-3 exopolysaccharide treatment. Additionally, the genes involved in metabolisms of amino acids, carbohydrates, lipids and nucleotides, varied to certain degrees. B-3 exopolysaccharide, therefore, appears to directly affect the immune function of RAW264.7 macrophages as an immunostimulant, or to indirectly change intracellular metabolism. This is the first study to determine the effect of an Antarctic psychrophilic bacterial exopolysaccharide on RAW264.7 macrophages. Our findings provide an important reference for research into the regulation of macrophage immune function by different polysaccharides.展开更多
The design of variants to enhance conformational stability of proteins is an important aspect of protein engineering. Oligomeric proteins are often stabilized by aromatic clusters located within the subunit interfaces...The design of variants to enhance conformational stability of proteins is an important aspect of protein engineering. Oligomeric proteins are often stabilized by aromatic clusters located within the subunit interfaces. In the present study, the authors constructed five variants of Ps3aHSD （Pseudomonas sp. B-0831 3a-hydroxysteroid dehydrogenase） in which one or two residues at the dimer interface were replaced with aromatic residues, and examined the effects of introducing aromatic residues in this region on protein thermostability. Under their experimental conditions, all variants formed dimers, similar to wild-type Ps3aHSD. Thermal denaturation experiments indicated that Tm of all variants was 0.2-16.2 °C lower than that of wild-type protein, indicating less stable thanwild-type protein. The results collectively suggest that aromatic residues of natural oligomeric proteins are strictly posted in the interface to facilitate optimal interactions and avoid conformational strain.展开更多
基金The Important National Science&Technology Specific Projects under contract No.2011ZX8001-003the National Natural Science Fundation of China under contract No.40706053Chinese Polar Environment Comprehensive Investigation&Assessment Programs under contract No.CHINARE2017-01-05
文摘B-3 exopolysaccharide is extracted from the Antarctic psychrophilic bacterium Psychrobacter sp. B-3. We have previously shown that it activates macrophages and affects their immunoregulatory activities. To determine what genes are affected during this process, we detected the genes differentially expressed in cells of RAW264.7 macrophages treated with B-3 exopolysaccharide by transcriptomic analysis. B-3 exopolysaccharide treatment caused differential expression of 420 genes, of which 178 were up-regulated and 242 were down-regulated. These genes were shown to be involved in many aspects of cell function, mainly metabolism and immunity. Genes were enriched in multiple immune-related pathways, and the most significantly enriched genes were involved in antigen processing and presentation pathways. The pathway in which differentially expressed genes were the most significantly enriched was the metabolic pathway; specifically, the expression of many metabolic enzyme genes was altered by B-3 exopolysaccharide treatment. Additionally, the genes involved in metabolisms of amino acids, carbohydrates, lipids and nucleotides, varied to certain degrees. B-3 exopolysaccharide, therefore, appears to directly affect the immune function of RAW264.7 macrophages as an immunostimulant, or to indirectly change intracellular metabolism. This is the first study to determine the effect of an Antarctic psychrophilic bacterial exopolysaccharide on RAW264.7 macrophages. Our findings provide an important reference for research into the regulation of macrophage immune function by different polysaccharides.
文摘The design of variants to enhance conformational stability of proteins is an important aspect of protein engineering. Oligomeric proteins are often stabilized by aromatic clusters located within the subunit interfaces. In the present study, the authors constructed five variants of Ps3aHSD （Pseudomonas sp. B-0831 3a-hydroxysteroid dehydrogenase） in which one or two residues at the dimer interface were replaced with aromatic residues, and examined the effects of introducing aromatic residues in this region on protein thermostability. Under their experimental conditions, all variants formed dimers, similar to wild-type Ps3aHSD. Thermal denaturation experiments indicated that Tm of all variants was 0.2-16.2 °C lower than that of wild-type protein, indicating less stable thanwild-type protein. The results collectively suggest that aromatic residues of natural oligomeric proteins are strictly posted in the interface to facilitate optimal interactions and avoid conformational strain.
