Myxococcus CsgA,Drosophila Sniffer,and human HSD10 are cardiolipin phospholipases

Myxococcus xanthus development requires CsgA, a member of the short-chain alcohol dehydrogenase (SCAD) family of proteins. We show that CsgA and SocA, a protein that can replace CsgA function in vivo, oxidize the 2′-OH glycerol moiety on cardiolipin and phosphatidylglycerol to produce diacylglycerol (DAG), dihydroxyacetone, and orthophosphate. A lipid extract enriched in DAGs from wild-type cells initiates development and lipid body production in a csgA mutant to bypass the mutational block. This novel phospholipase C-like reaction is widespread. SCADs that prevent neurodegenerative disorders, such as Drosophila Sniffer and human HSD10, oxidize cardiolipin with similar kinetic parameters. HSD10 exhibits a strong preference for cardiolipin with oxidized fatty acids. This activity is inhibited in the presence of the amyloid β peptide. Three HSD10 variants associated with neurodegenerative disorders are inactive with cardiolipin. We suggest that HSD10 protects humans from reactive oxygen species by removing damaged cardiolipin before it induces apoptosis.     

黏球菌产生的活性天然产物

从化学结构、生物学活性、生物合成、应用开发等角度,综述了已有文献报道的黏球菌活性天然产物,重点介绍了作用于肌动蛋白的大环内酯类化合物rhizopodin、作用于呼吸链的肽类化合物myxothiazol和多烯类化合物myxalamid、作用于核酸的芳香类化合物myxopyronin和saframycin Mx1,以及作用于细胞壁的大环类化合物myxovirescin,阐明了黏球菌次级代谢产物的化学结构多样性和生物活性多样性,为进一步开发黏球菌活性天然产物提供线索。     

黏细菌总蛋白质组双向电泳条件的建立

目的 :建立可以对黏细菌蛋白质组进行阵列分离的双向电泳条件。方法 :以黏细菌模式菌株DK162 2为材料 ,不同方法制备DK162 2在营养性生长阶段的蛋白质组样品 ,双向电泳阵列菌体总蛋白。通过不同条件下电泳图谱的比较建立蛋白质组样品的制备方法和双向电泳的技术条件。结果 :两性离子去污剂CHAPS及还原剂的浓度是影响双向电泳图谱分辨力的重要因素 ;蛋白质组样品的处理必须在低温下快速完成 ,以避免蛋白降解。结论 :初步建立了黏细菌总蛋白质组的双向电泳条件 ,为在细胞水平分析该模式生物发育时期蛋白表达谱奠定了基础     

Unidirectional Movement of Flares of Cells of Myxococcus xanthus

Amongst other modes, Myxococcal cells move in swarms that are flares or columns of cells. It has been argued that this is a strategy allowing a large enough number of them to encounter food bacteria. Then, the combined large amount of extracellular lytic enzymes from the mass of cells can provide adequate nutrient resources from the food bacteria for all the myxococci of the swarm. However, how they move as a coherent column has not been adequately explained.

Here based on the idea that a rare cell can experience a special mutation such that it moves only unidirectionally, a proposal to account for this aspect of Myxococcus cell movement is suggested. Although wild type individual organisms of this species engage in forward and back movements, a mutant cell that moves unidirectionally can bias the movement of associated wild type cells and lead to the formation of a column of cells, headed by such a unique mutated cell. The non-mutated cells follow along it is suggested because of the S-motility (or social motility) system. This may link them to this single unidirectionally moving mutant cell to give a coherent movement to the column. This proposed type of mutation back mutates to wild type and the column no longer functions as such and only wild-type cells are present.     

Enhancement of dietary protein digestion by conjugated bile acids

BACKGROUND & AIMS: Conjugated bile acids promote absorption of dietary lipids by solubilizing them in mixed micelles. Bile acids are not considered to facilitate the digestion of other nutrients. METHODS: The effect of conjugated bile acids on the rate of protein hydrolysis by trypsin and chymotrypsin was examined in vitro. Common dietary proteins and 2 bacterial glutenases (proposed oral therapies for celiac sprue) were proteolyzed in the absence or presence of a 10 mmol/L conjugated bile acid mixture, simulating human bile composition. Lipolysis products (monoolein) and fatty acid were also evaluated to simulate postprandial intestinal contents. RESULTS: Conjugated bile acids dramatically enhanced the proteolysis of several dietary proteins, including beta-lactoglobulin, bovine serum albumin, myoglobin, and a commercially available dietary protein supplement. For beta-lactoglobulin, a cow's milk allergen that is resistant to pepsin cleavage, bile acids enhanced its proteolysis by pancreatic proteases even after incubation under gastric conditions. Exposure of prolyl endopeptidases to bile acids made them more susceptible to pancreatic proteases under simulated intestinal conditions. The conjugated bile acid effect was most pronounced in the presence of dihydroxy bile acids and was observable at bile concentrations below the critical micellar concentration but to a much greater extent at concentrations above the critical micellar concentration. CONCLUSIONS: We propose that, in addition to promoting lipid absorption, conjugated bile acids affect the digestion and assimilation of dietary proteins by accelerating hydrolysis by pancreatic proteases. These findings have implications for intraluminal protein breakdown and assimilation in the upper small intestine.     

黏球菌产生的活性天然产物

从化学结构、生物学活性、生物合成、应用开发等角度,综述了已有文献报道的黏球菌活性天然产物,重点介绍了作用于肌动蛋白的大环内酯类化合物rhizopodin、作用于呼吸链的肽类化合物myxothiazol和多烯类化合物myxalamid、作用于核酸的芳香类化合物myxopyronin和saframycin Mx1,以及作用于细胞壁的大环类化合物myxovirescin,阐明了黏球菌次级代谢产物的化学结构多样性和生物活性多样性,为进一步开发黏球菌活性天然产物提供线索。