残基相互作用网络特征与木聚糖酶耐热性的关系

残基相互作用网络是体现蛋白质中残基与残基之间协同和制约关系的重要形式。残基相互作用网络的拓扑性质以及社团结构与蛋白质的功能和性质有密切的关系。本文在构建一系列耐热木聚糖酶和常温木聚糖酶的残基相互作用网络后，通过计算网络的度、聚类系数、连接强度、特征路径长度、接近中心性、介数中心性等拓扑参数来确定网络拓扑结构与木聚糖酶耐热性的关系。识别残基相互作用网络的hub点，分析hub点的亲疏水性、带电性以及各种氨基酸在hub点中所占的比例。进一步使用GA-Net算法对网络进行社团划分，并计算社团的规模、直径和密度。网络的高平均度、高连接强度、以及更短的最短路径等表明耐热木聚糖酶残基相互作用网络的结构更加紧密；耐热木聚糖酶网络中的hub节点比常温木聚糖酶网络hub节点具有更多的疏水性残基，hub点中Phe、Ile、Val的占比更高。社团检测后发现，耐热木聚糖酶网络拥有更大的社团规模、较小的社团直径和较大的社团密度。社团规模越大表明耐热木聚糖酶的氨基酸残基更倾向于形成大的社团，而较小的社团直径和较大的社团密度则表明社团内部氨基酸残基的相互作用比常温木聚糖酶更强。

Relationship Between the Characteristics of Residue Interaction Network and Xylanase Heat Resistance

The residue interaction network is an effective form of the relationship between amino acid residues in the proteins. The topological properties of residue interaction networks and the community structure are closely related to the function and properties of proteins. In this paper, after constructing a series of thermophilic xylanase and mesophilic xylanase residue interaction networks, the relationship between the network topology structure and xylanase heat resistance was determined by calculating the topological parameters, such as network degree, clustering coefficient, connection strength, characteristic path length, closeness centrality, betweenness centrality, etc. The hubs of the residue interaction network were identified, and the hydrophilicity and electrical properties of them were analyzed. The proportion of amino acids in the hub sites was also analyzed. Furthermore, the GA-Net algorithm is used to divide the network to find communities. The size, diameter and density of the communities are calculated. Higher average, higher connection strength, and shorter shortest path indicate that the network structure of the thermophilic xylanase residue interaction networks are tighter. The hubs in the thermophilic xylanase networks have more hydrophobic residues than in the mesophilic xylanase networks, and the proportion of Phe, Ile and Val in the hubs are higher than that of mesophilic ones. The communities show that the thermophilic xylanase networks have a larger community size, smaller community diameter and larger community density. The larger community size indicates that the more the amino acid residues of the thermophilic xylanase are tend to form a large community. The smaller community diameter and larger community density indicate that the interactions of residues within the thermophilic xylanase community are stronger than that of the mesophilic xylanase.