Ilari Andrea, Fiorillo Annarita, Angelaccio Sebastiana, Florio Rita, Chiaraluce Roberta, van der Oost John, Consalvi Valerio
CNR Institute of Molecular Biology and Pathology, Italy.
FEBS J. 2009 Feb;276(4):1048-58. doi: 10.1111/j.1742-4658.2008.06848.x. Epub 2008 Jan 16.
Bacterial and archaeal endo-beta-1,3-glucanases that belong to glycoside hydrolase family 16 share a beta-jelly-roll fold, but differ significantly in sequence and in substrate specificity. The crystal structure of the laminarinase (EC 3.2.1.39) from the hyperthermophilic archaeon Pyrococcus furiosus (pfLamA) has been determined at 2.1 A resolution by molecular replacement. The pfLamA structure reveals a kink of six residues (72-77) at the entrance of the catalytic cleft. This peptide is absent in the endoglucanases from alkaliphilic Nocardiopsis sp. strain F96 and Bacillus macerans, two proteins displaying an overall fold similar to that of pfLamA, but with different substrate specificity. A deletion mutant of pfLamA, lacking residues 72-75, hydrolyses the mixed-linkage beta-1,3-1,4-glucan lichenan 10 times more efficiently than the wild-type protein, indicating the importance of the kink in substrate preference.
属于糖苷水解酶家族16的细菌和古菌内切β-1,3-葡聚糖酶具有β-果冻卷折叠结构，但在序列和底物特异性上有显著差异。嗜热古菌激烈火球菌（Pyrococcus furiosus）的海带多糖酶（EC 3.2.1.39，即pfLamA）的晶体结构已通过分子置换法在2.1埃分辨率下测定。pfLamA的结构显示，在催化裂隙入口处有一个由六个残基（72 - 77）组成的扭结。嗜碱诺卡氏菌属（Nocardiopsis sp.）菌株F96和软化芽孢杆菌（Bacillus macerans）的内切葡聚糖酶中不存在这个肽段，这两种蛋白质的整体折叠结构与pfLamA相似，但底物特异性不同。pfLamA的一个缺失突变体，缺少残基72 - 75，其水解混合连接的β-1,3-1,4-葡聚糖地衣多糖的效率比野生型蛋白高10倍，这表明该扭结对底物偏好具有重要性。
