Institute of Technical Microbiology, Hamburg University of Technology, Kasernenstr. 12, 21073 Hamburg, Germany.
Extremophiles. 2011 Mar;15(2):311-7. doi: 10.1007/s00792-011-0361-8. Epub 2011 Feb 18.
The OsmC-region (osmotically induced protein family) of the two-domain esterase EstO from the psychrotolerant bacterium Pseudoalteromonas arctica has been shown to increase thermolability. In an attempt to test if these properties can be conferred to another enzyme, we genetically fused osmC to the 3'-region of the family 8 xylanase encoding gene xyn8 from P. arctica. The chimeric open reading frame xyn8-OsmC was cloned and the chimeric protein was purified after heterologous expression in Escherichia coli. Xyn8 and Xyn8-OsmC showed cold-adapted properties (more than 60% activity at 0°C) using birchwood xylan as the preferred substrate. Maximal catalytic activity is slightly shifted from 15°C (Xyn8) to 20°C for Xyn8-OsmC. Thermostability of Xyn8-OsmC is significantly changed in comparison to wild-type Xyn8. The OsmC-fusion variant showed an apparent decrease in thermostability between 40 and 45°C, while both proteins are highly instable at 50°C.
来自耐冷细菌北极假交替单胞菌的双域酯酶 EstO 的 OsmC 区域（渗透诱导蛋白家族）已被证明会增加热不稳定性。为了测试这些特性是否可以赋予另一种酶，我们将 osmC 基因融合到家族 8 木聚糖酶编码基因 xyn8 的 3'区域。嵌合开放阅读框 xyn8-OsmC 被克隆，并且在大肠杆菌中异源表达后纯化嵌合蛋白。Xyn8 和 Xyn8-OsmC 显示出冷适应特性（在 0°C 下活性超过 60%），以桦木木聚糖为首选底物。最大催化活性略有从 15°C（Xyn8）转移到 20°C（Xyn8-OsmC）。与野生型 Xyn8 相比，Xyn8-OsmC 的热稳定性发生了显著变化。与 OsmC 融合变体相比，OsmC 融合变体在 40°C 和 45°C 之间的热稳定性明显下降，而两种蛋白质在 50°C 时都非常不稳定。
