Department of Biotechnology and Biosciences, State University of Milano-Bicocca, Italy.
Institute of Biochemistry, Food Science and Nutrition, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
FEBS J. 2017 Jan;284(1):163-177. doi: 10.1111/febs.13965. Epub 2016 Dec 26.
Cold environments are populated by organisms able to contravene deleterious effects of low temperature by diverse adaptive strategies, including the production of ice binding proteins (IBPs) that inhibit the growth of ice crystals inside and outside cells. We describe the properties of such a protein (EfcIBP) identified in the metagenome of an Antarctic biological consortium composed of the ciliate Euplotes focardii and psychrophilic non-cultured bacteria. Recombinant EfcIBP can resist freezing without any conformational damage and is moderately heat stable, with a midpoint temperature of 66.4 °C. Tested for its effects on ice, EfcIBP shows an unusual combination of properties not reported in other bacterial IBPs. First, it is one of the best-performing IBPs described to date in the inhibition of ice recrystallization, with effective concentrations in the nanomolar range. Moreover, EfcIBP has thermal hysteresis activity (0.53 °C at 50 μm) and it can stop a crystal from growing when held at a constant temperature within the thermal hysteresis gap. EfcIBP protects purified proteins and bacterial cells from freezing damage when exposed to challenging temperatures. EfcIBP also possesses a potential N-terminal signal sequence for protein transport and a DUF3494 domain that is common to secreted IBPs. These features lead us to hypothesize that the protein is either anchored at the outer cell surface or concentrated around cells to provide survival advantage to the whole cell consortium.
寒冷环境中生存着各种生物，它们通过多种适应性策略来抵抗低温的有害影响，包括产生冰结合蛋白（IBP），抑制冰晶在细胞内外的生长。我们描述了一种在由纤毛虫 Euplotes focardii 和嗜冷未培养细菌组成的南极生物联合体的宏基因组中发现的这种蛋白质（EfcIBP）的特性。重组 EfcIBP 可以在没有任何构象损伤的情况下抵抗冷冻，并且具有适度的热稳定性，中点温度为 66.4°C。在测试其对冰的影响时，EfcIBP 表现出了与其他细菌 IBP 不同的特性组合。首先，它是迄今为止在抑制冰晶重结晶方面表现最好的 IBP 之一，其有效浓度在纳摩尔范围内。此外，EfcIBP 具有热滞活性（在 50 µm 时为 0.53°C），当在热滞间隙内保持恒定温度时，它可以阻止晶体生长。当暴露于具有挑战性的温度时，EfcIBP 可保护纯化的蛋白质和细菌细胞免受冷冻损伤。EfcIBP 还具有用于蛋白质运输的潜在 N 端信号序列和常见于分泌 IBP 的 DUF3494 结构域。这些特征使我们假设该蛋白要么锚定在细胞外表面，要么在细胞周围浓缩，为整个细胞联合体提供生存优势。
