黑曲霉内切β-木聚糖酶三维结构模建及分子进化分析

Homology Modeling and Molecular Evolution Analysis of Endo-1,4-β-xylanase from Aspergillus niger

内切β-木聚糖酶是一类木聚糖降解酶,对黑曲霉来源的内切β-木聚糖酶核酸序列进行序列比对,构建进化树;采用同源模建方法模建内切β-木聚糖酶的三级结构,并预测内切β-木聚糖酶的二级结构。进化树将内切β-木聚糖酶分成3个组:第1组和第2组的3-D结构相似,而第3组的3-D结构和前2者差别较大。第1组含有1个α-螺旋和13个β-折叠二级结构,二硫键位于Cys119和Cys138之间;第2组含有1个α-螺旋和13个β-折叠二级结构;第3组含有13个α-螺旋、3个3,10-螺旋和9个β-折叠二级结构,二硫键位于Cys281和Cys287之间,而且第3组还含有一个复杂的β-α-β结构域。该研究为黑曲霉内切β-木聚糖酶的结构,功能和蛋白质工程研究提供了一定的理论基础。

Endo- 1,4- beta- xylanase is one of the most important enzymes which are involved in the hydrolysis of xylan polymers, and these enzymes degrade xylan to short chain xylo - oligosaecharides of varying lengths. The multiple sequence alignment of the available endo - 1,4 - β -xylanase eDNA sequences and the related evolutionary analyses were performed; the 3 - D structures of the endo - 1,4 -β- xylanase was built using homology mode/ling technique. The phylogenetic tree revealed that there were three group ： the sequence of the third group enzyme is different from the sequence of the first group enzyme which is the same as the sequence from the second group enzyme. The structure of the first group enzyme comprises a single domain and contains one a - he/ix, 13 β - strands and one disulphide bridges Cys119 - Cys138 ; The second had one a - helix and 13 13 - strands; The third had 13 a - helix, three 3,10 - helix, 9 β - strands and one disulphide bridges Cys281 - Cys287. Furthermore, The third also had β - α - β motif. This paper could help for the study in the structure, function and enzyme engineering of the endo - 1,4 - β - xylanase.