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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >A nonprotein thermal hysteresis-producing xylomannan antifreeze in the freeze-tolerant Alaskan beetle Upis ceramboides
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A nonprotein thermal hysteresis-producing xylomannan antifreeze in the freeze-tolerant Alaskan beetle Upis ceramboides

机译：耐冷冻的阿拉斯加甲虫Upis ceramboides中产生非蛋白质热滞的木糖甘露聚糖防冻剂

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摘要

Thermal hysteresis (TH), a difference between the melting and freezing points of a solution that is indicative of the presence of large-molecular-mass antifreezes (e.g., antifreeze proteins), has been described in animals, plants, bacteria, and fungi. Although all previously described TH-producing biomolecules are proteins, most thermal hysteresis factors (THFs) have not yet been structurally characterized, and none have been characterized from a freeze-tolerant animal. We isolated a highly active THF from the freeze-tolerant beetle, Upis ceramboides, by means of ice affinity. Amino acid chromatographic analysis, polyacrylamide gel electro-phoresis, UV-Vis spectrophotometry, and NMR spectroscopy indicated that the THF contained little or no protein, yet it produced 3.7 ± 0.3 ℃ of TH at 5 mg/ml, comparable to that of the most active insect antifreeze proteins. Compositional and structural analyses indicated that this antifreeze contains a β-mannopyranosyl-(1→4) β-xylopyranose backbone and a fatty acid component, although the lipid may not be covalently linked to the saccharide. Consistent with the proposed structure, treatment with endo-β-(1→4)xyla-nase ablated TH activity. This xylomannan is the first TH-producing antifreeze isolated from a freeze-tolerant animal and the first in a new class of highly active THFs that contain little or no protein.
机译：已经在动物，植物，细菌和真菌中描述了热滞后（TH），其是溶液的熔点和凝固点之间的差异，表明存在大分子抗冻剂（例如抗冻蛋白）。尽管所有先前描述的产生TH的生物分子都是蛋白质，但是大多数热滞后因子（THF）尚未在结构上得到表征，并且没有从耐冻动物中得到任何表征。我们通过冰亲和力从耐冻甲虫Upis ceramboides中分离出了高活性的THF。氨基酸色谱分析，聚丙烯酰胺凝胶电泳，UV-Vis分光光度法和NMR光谱表明，THF所含蛋白质很少或不包含蛋白质，但它在5 mg / ml时产生的3.7±0.3℃TH相当于大多数活性昆虫抗冻蛋白。组成和结构分析表明，该防冻液包含β-甘露聚糖基（1→4）β-吡喃葡萄糖主链和脂肪酸成分，尽管脂质可能未与糖共价连接。与拟议的结构一致，内切-β-（1→4）木聚糖酶处理可降低TH活性。该木糖甘露聚糖是从耐冻动物中分离出的第一种产生TH的防冻剂，并且是新型的几乎不含或几乎不含蛋白质的高活性THF。

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