摘要
【目的】解析Streptomyces sp.DJ菌株编码的3种角蛋白酶的氨基酸序列、二级结构、三级结构及其功能的关系。【方法】基于DJ菌株全基因组测序结果,利用Bio-edit、DNAMAN、Discovery Studio2.5等软件、https://swissmodel.expasy.org/等网站对其3种角蛋白酶的序列和结构进行了分析和预测。【结果】DJ菌株胞外分泌3种角蛋白酶(K1、K2和K3)均属于S8家族的丝氨酸蛋白酶,信号肽、前导肽和成熟肽在氨基酸残基的组成、极性和长度等方面较一致。3种酶均能以5WSL.1.A为模板进行同源建模,每种酶的3-D结构中均含有6个α螺旋、2个3_(10)α螺旋和15个β折叠的二级结构;其中K1酶含有2个二硫键,1Ca和2Ca位点,K2和K3各有1个二硫键,1Ca位点;3种酶的Pro270残基位于loop环,而仅有K2的Pro242残基位于loop环中。3种酶底物结合区域主要由疏水性残基构成,偏向于疏水性强的底物。3种酶的底物结合区域比较而言,S1和S2对底物特异性起关键作用;由于3种酶的S1和S2中重要位点残基的不保守性,使其底物特异性具有差异。【结论】DJ菌株中3种角蛋白酶在氨基酸、二硫键、脯氨酸和钙结合等的不同致使酶稳定性的不同;并且由于其表面电荷分布、底物结合区域的差异构成对羽毛水解位点的互补性,这可能是DJ菌株高效降解羽毛的重要原因。
【Objective】The present study aimed to reveal the relationship between the amino acid sequence,secondary structure,tertiary structure and their functions of the three keratinases produced by the Streptomyces sp.DJ strain.【Method】Based on whole genome sequencing results of DJ strain,the sequence and structure of its three keratinases were analyzed and predicted by using software,such as Bio-edit,DNAMAN,Discovery Studio2.5 et al,and website like https://swissmodel.expasy.org/,and so on.【Result】DJ strains secreted three kinds of keratinases(K1,K2 and K3),and the keratinases belonged to serine proteases of the S8 family,and their signal peptides,leading peptides and mature peptides were more consistent in the composition,polarity and length of amino acid residues.Three keratinases were modeled using 5 WSL.1.A as template by the homology modeling technique.The 3-D structure of each keratinase contained sixα-helix,two 3_(10)-helix and fifteenβ-folded secondary structures.K1 contained two disulfide bonds,1 Ca and 2 Ca sites,while K2 and K3 had only one disulfide bond and 1 Ca site.The Pro270 residues of all three keratinases were respectively located in the loop ring,while only Pro242 residue of K2 was also located in the loop ring.The substrates binding regions of the three keratinases were mainly composed of hydrophobic residues,so these keratinases preferred substrate with strong hydrophobicity.For the substrate binding regions of the keratinases,the S1 and S2 played a key role in substrate specificity.And the substrate specificity was different due to the non-conservative nature of the residues at important sites in the S1 and S2 of the three keratinases.【Conclusion】The differences in amino acid,disulfide bond,proline and calcium binding sites leaded to the different stability of the three keratinases,besides the surface charge distribution and substrate binding regions resulted the complementarity to the feather hydrolysis sites.This might be an important reason for the efficient degradation of feathers by DJ strains.
作者
柯野
杨家臣
屈奇奇
袁小枚
黄镜如
KE Ye;YANG Jia-chen;QU Qi-qi;YUAN Xiao-mei;HUANG Jing-ru(Henry Fok College of Biology and Agriculture,Shaoguan University,Guangdong Shaoguan 512005,China)
出处
《西南农业学报》
CSCD
北大核心
2021年第10期2274-2280,共7页
Southwest China Journal of Agricultural Sciences
基金
广东省基础与应用基础研究基金(2019A1515011089)
韶关市科技计划项目(2018sn087)
2018韶关学院大学生创新创业训练计划国家级项目(201810576007)
广东大学生科技创新培育专项资金资助项目(pdjh2020b0536)。