论文部分内容阅读
采用 52℃下加热 6 min,后经 DEAE- 52、Sephacryls S- 2 0 0和 Q- Sepharose等柱层析方法 ,分离纯化了棕色固氮菌 (Azotobacter vinelandii)缺失 nif Z基因突变种固氮酶 Mo Fe(Δnif Z Mo Fe)蛋白 ,其纯度达到电泳纯。Δnif Z Mo Fe蛋白的固氮活性为 2 83nmol C2 H2 还原 / (min·mg蛋白 ) ,远低于野生种 Mo Fe蛋白。Δnif Z Mo Fe蛋白对氧更敏感 ;热稳定性略低于野生种。Δnif Z Mo Fe蛋白的可见光吸收光谱与野生种 Mo Fe蛋白极为相似。其圆二色谱和磁圆二色谱在 450～ 550 nm与野生种 Mo Fe蛋白显著不同 ,表明其 P- cluster及其周围环境与野生种 Mo Fe蛋白有所差异。这亦可能是造成缺失 nif Z突变种 Mo Fe蛋白固氮活性低的原因。
After heating at 52 ℃ for 6 min, the Nif Z gene mutant Azotobacter vinelandii, which is a mutant of nitrogenase N, was isolated and purified by DEAE-52, Sephacryls S- 200 and Q-Sepharose column chromatography. (Δnif Z Mo Fe) protein, its purity reaches electrophoresis pure. The nitrogen fixation activity of Δnif Z Mo Fe protein was 2 83 nmol C2 H2 reduction / (min · mg protein), much lower than that of wild-type Mo Fe protein. The Δnif Z Mo Fe protein is more sensitive to oxygen; its thermal stability is slightly lower than that of wild species. The visible light absorption spectrum of Δnif Z Mo Fe protein is very similar to that of wild-type Mo Fe protein. Circular dichroism and circular dichroism were significantly different from those of the wild-type Mo Fe protein at 450-550 nm, indicating that the P-cluster and its surroundings are different from the wild-type Mo Fe protein. This may also be responsible for the low nitrogen fixation activity of the MoIF protein resulting in the absence of the nif Z mutant.