Department of Biomedical and Molecular Sciences, Queen's University, K7L 3N6, Kingston, ON, Canada.
The Robert H. Smith Faculty of Agriculture, Food and Environment, Institute of Biochemistry, Food Science, and Nutrition, The Hebrew University of Jerusalem, Rehovot, 7610001, Israel.
Nat Commun. 2022 Aug 26;13(1):5019. doi: 10.1038/s41467-022-32469-9.
Bacterial ice nucleation proteins (INPs) can cause frost damage to plants by nucleating ice formation at high sub-zero temperatures. Modeling of Pseudomonas borealis INP by AlphaFold suggests that the central domain of 65 tandem sixteen-residue repeats forms a beta-solenoid with arrays of outward-pointing threonines and tyrosines, which may organize water molecules into an ice-like pattern. Here we report that mutating some of these residues in a central segment of P. borealis INP, expressed in Escherichia coli, decreases ice nucleation activity more than the section's deletion. Insertion of a bulky domain has the same effect, indicating that the continuity of the water-organizing repeats is critical for optimal activity. The ~10 C-terminal coils differ from the other 55 coils in being more basic and lacking water-organizing motifs; deletion of this region eliminates INP activity. We show through sequence modifications how arrays of conserved motifs form the large ice-nucleating surface required for potency.
细菌冰核蛋白（INP）可以通过在高亚零度温度下引发冰形成来导致植物霜害。AlphaFold 对假单胞菌冰核蛋白的建模表明，由 65 个串联的 16 个残基重复组成的中心结构域形成一个β-螺线管，带有向外指向的苏氨酸和酪氨酸阵列，这些可能将水分子组织成类似冰的图案。在这里，我们报告说，在大肠杆菌中表达的假单胞菌冰核蛋白中央片段中突变一些这些残基会使冰核活性降低超过该片段的缺失。插入一个大的结构域也有同样的效果，表明水分子组织重复的连续性对于最佳活性至关重要。大约 10 个 C 端螺旋与其他 55 个螺旋不同，它们更碱性且缺乏水分子组织基序；删除该区域会消除 INP 活性。我们通过序列修饰展示了保守基序的阵列如何形成用于效力的大冰核表面。
