Kumasaka T, Yamamoto M, Moriyama H, Tanaka N, Sato M, Katsube Y, Yamakawa Y, Omori-Satoh T, Iwanaga S, Ueki T
Department of Life Science, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama.
J Biochem. 1996 Jan;119(1):49-57. doi: 10.1093/oxfordjournals.jbchem.a021215.
The crystal structure of the zinc-protease, H2-proteinase, isolated from the venom of Trimeresurus flavoviridis has been determined. The crystallographic R factor is 0.176 for 10,635 reflections with Fobs > 2sigma(Fobs) in the 8.0 to 2.2 Angstrom resolution range. The enzyme has two domains with a cleft in which a catalytic zinc atom is located. The N-terminal domain is composed of four helices around a central five-stranded beta-sheet. The irregularly folded C-terminal domain contains one helix and two disulfide bridges. These two domains are linked by a disulfide bridge. In the zinc environment, the catalytic zinc atom forms a distorted tetrahedral coordination with three histidines and one catalytic water molecule, and the methionine-containing turn is structurally conserved. These are distinctive features of the metzincins, one of the zinc metalloprotease superfamilies. The entire structure shows good agreement with that of two Crotalus snake venom proteases, adamalysin II and atrolysin C. The H2-proteinase, however, contains no structural calcium ions, and differences of disulfide configurations and the coordination of the catalytic water molecule exist as compared with the other two proteases.
已确定从竹叶青蛇毒液中分离出的锌蛋白酶H2-蛋白酶的晶体结构。在8.0至2.2埃分辨率范围内，对于10,635个Fobs > 2sigma(Fobs)的反射，晶体学R因子为0.176。该酶有两个结构域，中间有一个裂隙，催化锌原子位于其中。N端结构域由围绕中央五链β折叠的四个螺旋组成。不规则折叠的C端结构域包含一个螺旋和两个二硫键。这两个结构域通过一个二硫键相连。在锌环境中，催化锌原子与三个组氨酸和一个催化水分子形成扭曲的四面体配位，含蛋氨酸的转角在结构上保守。这些是金属锌蛋白酶超家族之一的金属锌内肽酶的独特特征。整个结构与两种响尾蛇蛇毒蛋白酶——解整合素金属蛋白酶II和锯鳞蝰素C的结构吻合良好。然而，H2-蛋白酶不含结构钙离子，与其他两种蛋白酶相比，其二硫键构型和催化水分子的配位存在差异。
