Wu Zhongqin, Qin Lei, Walker Virginia K
Department of Biology, Kingston, ON K7L 3N6, Canada.
Department of Microbiology and Immunology, Kingston, ON K7L 3N6, Canada.
Microbiology (Reading). 2009 Apr;155(Pt 4):1164-1169. doi: 10.1099/mic.0.025114-0.
Isolates of 'Pseudomonas borealis' were recovered after ice-affinity selection of summer-collected soils. 'P. borealis' DL7 was further characterized and shown to have ice nucleation activity (INA), a property that allows the crystallization of ice at temperatures close to the melting point, effectively preventing the supercooling of water. INA was optimally detected after culturing at temperatures consistent with psychrophilic growth. The sequence encoding the 'P. borealis' ice nucleation protein (INP) was obtained using both PCR and chromosome walking. When expressed in Escherichia coli, the resulting inaPb recombinants had INA. The 'P. borealis' sequence, dubbed inaPb, is clearly related to previously cloned INP genes, but it shows greater divergence. Sequence analysis suggests that there are two opposite flat surfaces, one relatively hydrophobic that likely serves as an ice template, and the other that could function as a complementary face to facilitate interprotein interaction for ice-step formation.
通过对夏季采集的土壤进行冰亲和性筛选，分离出了“北方假单胞菌”菌株。对“北方假单胞菌”DL7进行了进一步表征，结果表明其具有冰核活性（INA），这种特性使得冰在接近熔点的温度下结晶，有效防止了水的过冷现象。在与嗜冷生长一致的温度下培养后，能最佳地检测到冰核活性。使用聚合酶链反应（PCR）和染色体步移技术获得了编码“北方假单胞菌”冰核蛋白（INP）的序列。当在大肠杆菌中表达时，产生的inaPb重组体具有冰核活性。被称为inaPb的“北方假单胞菌”序列与先前克隆的INP基因明显相关，但差异更大。序列分析表明存在两个相对的平面，一个相对疏水，可能作为冰模板，另一个可能作为互补面，以促进蛋白质间相互作用形成冰阶。
