The mutated nickase Nt.BspD6I E418A has been obtained by site-directed mutagenesis. The purified protein has been crystallized, and its spatial structure has been determined at 2.45 Å resolution. An analysis of the crystal structures of the wild-type and mutated nickase have shown that the elimination of a carboxyl group due to the E418A mutation initiates marked conformational changes in both the N-terminal recognition domain and the C-terminal catalytic domain of nickase and insignificantly affects its linker domain. This is supported by changes in the functional properties of mutated nickase: an increase in the oligomerization capacity in the presence of a substrate, a reduction in the capacity to bind a substrate, and complete loss of catalytic activity.

中文翻译：

---

E418羧基在Nt.BspD6I切口酶活性位点形成中的关键作用：Nt.BspD6I E418A突变体的结构和功能特性。

已通过定点诱变获得了突变的切口酶Nt.BspD6I E418A。纯化的蛋白质已结晶，其空间结构已确定为2.45Å分辨率。对野生型和突变的切口酶的晶体结构的分析表明，由于E418A突变而导致的羧基消除会在切口酶的N端识别域和C端催化域中引发明显的构象变化。对它的链接器域影响不大。这由突变切口酶的功能性质的改变来支持：在存在底物的情况下寡聚能力的增加，与底物结合的能力的降低以及催化活性的完全丧失。