Tachioka Mikako, Nakamura Akihiko, Ishida Takuya, Igarashi Kiyohiko, Samejima Masahiro
Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Acta Crystallogr F Struct Biol Commun. 2017 Jul 1;73(Pt 7):398-403. doi: 10.1107/S2053230X17008093. Epub 2017 Jun 17.
Cellobiohydrolases belonging to glycoside hydrolase family 6 (CBH II, Cel6A) play key roles in the hydrolysis of crystalline cellulose. CBH II from the white-rot fungus Phanerochaete chrysosporium (PcCel6A) consists of a catalytic domain (CD) and a carbohydrate-binding module connected by a linker peptide, like other known fungal cellobiohydrolases. In the present study, the CD of PcCel6A was crystallized without ligands, and p-nitrophenyl β-D-cellotrioside (pNPG3) was soaked into the crystals. The determined structures of the ligand-free and pNPG3-soaked crystals revealed that binding of cellobiose at substrate subsites +1 and +2 induces a conformational change of the N-terminal and C-terminal loops, switching the tunnel-shaped active site from the open to the closed form.
属于糖苷水解酶家族6的纤维二糖水解酶（CBH II，Cel6A）在结晶纤维素的水解中起关键作用。来自白腐真菌黄孢原毛平革菌的CBH II（PcCel6A）与其他已知的真菌纤维二糖水解酶一样，由一个催化结构域（CD）和一个通过连接肽连接的碳水化合物结合模块组成。在本研究中，PcCel6A的CD在没有配体的情况下结晶，然后将对硝基苯基β-D-纤维三糖苷（pNPG3）浸泡到晶体中。无配体晶体和浸泡pNPG3晶体的测定结构表明，纤维二糖在底物亚位点+1和+2处的结合会诱导N端和C端环的构象变化，将隧道状活性位点从开放形式转变为封闭形式。
