Kurisu G, Kinoshita T, Sugimoto A, Nagara A, Kai Y, Kasai N, Harada S
Department of Applied Chemistry, Faculty of Engineering, Osaka University.
J Biochem. 1997 Feb;121(2):304-8. doi: 10.1093/oxfordjournals.jbchem.a021587.
A zinc endoprotease produced by Streptomyces caespitosus (ScNP) specifically hydrolyzes the peptide bond at the imino side of aromatic residues and is the smallest protease found to date. Although ScNP carries the zinc-binding sequence HEXXH, its primary structure of 132 amino acid residues differs from those of other known zinc metalloendoproteases. X-ray structural analysis of ScNP at 1.6 A resolution revealed that despite a lack of sequence homology, the common topological feature of main-chain folding and a beta-turn containing methionine, which is a feature of the zinc metalloendoprotease superfamily of metzincins, is conserved in ScNP. The zinc atom of ScNP is tetrahedrally ligated by the two histidines in the HEXXH sequence, an aspartate residue and a water molecule. Thus, ScNP represents a novel subfamily of metzincins with a HEXXHXXGXXD zinc-binding sequence. A plausible substrate recognition pocket to which aromatic residues bind is located near the catalytic zinc ion.
由丛生链霉菌产生的一种锌内蛋白酶（ScNP）特异性水解芳香族残基亚氨基侧的肽键，是迄今为止发现的最小的蛋白酶。尽管ScNP带有锌结合序列HEXXH，但其132个氨基酸残基的一级结构与其他已知的锌金属内蛋白酶不同。以1.6埃分辨率对ScNP进行的X射线结构分析表明，尽管缺乏序列同源性，但主链折叠的常见拓扑特征以及包含甲硫氨酸的β-转角（这是金属锌蛋白酶超家族metzincins的一个特征）在ScNP中是保守的。ScNP的锌原子由HEXXH序列中的两个组氨酸、一个天冬氨酸残基和一个水分子以四面体方式配位。因此，ScNP代表了一个具有HEXXHXXGXXD锌结合序列的metzincins新亚家族。一个芳香族残基结合的合理底物识别口袋位于催化锌离子附近。
