哈茨木霉酸性蛋白酶P6281的结构分析

Structure Analysis of Acidic Protease P6281 from Trichoderma Harzianum

利用生物信息学网站、软件对哈茨木霉酸性蛋白酶P6281进行了预测和分析.结果表明,P6281属于Clan AA中A1家族的天冬氨酸蛋白酶,一级结构是由386个氨基酸残基组成的序列,其中序列的氨基酸残基1~17位为信号肽、18~65位为前导肽、66~386位为成熟肽.以来源于Irpex lacteus的天冬氨酸蛋白酶(PDB code:1wkr.1.A)为模板进行同源建模;从构建的P6281模型中可知,P6281二级结构主要由β折叠以及少量的简短α螺旋结构组成.三级结构由类二重对称的N-lobe和C-lobe形成,该结构中无丝氨酸和脯氨酸形成的顺式肽键、loop环中无脯氨酸残基、无Zn离子结合、含有1个二硫键、270个氢键.N-lobe和C-lobe相结合的缝隙即为P6281的底物结合区域(分为S2’、S1’、S1、S2、S3和S4),其中S1’、S1、S3和S4对其底物选择性具有关键性作用;并且底物结合区域中重要位点的氨基酸残基的保守性和差异性,决定了P6281对底物肽键选择性的独特性.

The acid protease P6281 from Trichoderma harzianum was predicted and analyzed by using bioinformatics websites and software.The results showed P6281 belonged to the A1 family aspartic protease in Clan AA.The primary structure was a sequence composed of 386 amino acid residues,of which 1~17 was a signal peptide,18~65 was a leading peptide and 66~386 was a mature peptide.Using aspartic protease(PDB code:1wkr.1.A)from Irpex lacteus as a template,P6281 model was built by homologous modeling.According to the model,the secondary structure of P6281 was mainly composed ofβFolding,and a small amount of shortαhelix structure.The tertiary structure was formed by double symmetric N-lobes and C-lobes.The structure had no SP cis peptide bond,no proline residue in loop ring,no Zn ion binding,one disulfide bond and 270 hydrogen bonds.The gap between N-lobes and C-lobes was the substrate binding region of P6281(divided into S2’,S1’,S1,S2,S3 and S4),in which S1’,S1,S3 and S4 played a key role in its substrate selectivity;moreover,the conservation and difference of amino acid residues at important sites in the substrate binding region determined the uniqueness of P6281 for substrate peptide bond selectivity.