Nascimento Alessandro S, Muniz Joao Renato C, Aparício Ricardo, Golubev Alexander M, Polikarpov Igor
Instituto de Física de São Carlos, Universidade de São Paulo, Brazil.
FEBS J. 2014 Sep;281(18):4165-78. doi: 10.1111/febs.12894. Epub 2014 Jul 14.
Hemicellulose is an important part of the plant cell wall biomass, and is relevant to cellulosic ethanol technologies. β-Mannosidases are enzymes capable of cleaving nonreducing residues of β-d-mannose from β-d-mannosides and hemicellulose mannose-containing polysaccharides, such as mannans and galactomannans. β-Mannosidases are distributed between glycoside hydrolase (GH) families 1, 2, and 5, and only a handful of the enzymes have been structurally characterized to date. The only published X-ray structure of a GH family 2 mannosidase is that of the bacterial Bacteroides thetaiotaomicron enzyme. No structures of eukaryotic mannosidases of this family are currently available. To fill this gap, we set out to solve the structure of Trichoderma harzianum GH family 2 β-mannosidase and to refine it to 1.9-Å resolution. Structural comparisons of the T. harzianum GH2 β-mannosidase highlight similarities in its structural architecture with other members of GH family 2, reveal the molecular mechanism of β-mannoside binding and recognition, and shed light on its putative galactomannan-binding site.
Coordinates and observed structure factor amplitudes have been deposited with the Protein Data Bank (4CVU and 4UOJ). The T. harzianum β-mannosidase 2A nucleotide sequence has GenBank accession number BankIt1712036 GeneMark.hmm KJ624918.
半纤维素是植物细胞壁生物质的重要组成部分，与纤维素乙醇技术相关。β-甘露糖苷酶是能够从β-D-甘露糖苷和含半纤维素甘露糖的多糖（如甘露聚糖和半乳甘露聚糖）中切割β-D-甘露糖非还原端残基的酶。β-甘露糖苷酶分布在糖苷水解酶（GH）家族1、2和5中，迄今为止只有少数几种该酶的结构得到了表征。已发表的GH家族2甘露糖苷酶的唯一X射线结构是细菌嗜热栖热放线杆菌的酶的结构。目前尚无该家族真核甘露糖苷酶的结构。为了填补这一空白，我们着手解析哈茨木霉GH家族2β-甘露糖苷酶的结构，并将其精修至1.9 Å分辨率。哈茨木霉GH2β-甘露糖苷酶的结构比较突出了其与GH家族2其他成员在结构架构上的相似性，揭示了β-甘露糖苷结合和识别的分子机制，并阐明了其假定的半乳甘露聚糖结合位点。
坐标和观测到的结构因子振幅已存入蛋白质数据库（4CVU和4UOJ）。哈茨木霉β-甘露糖苷酶2A核苷酸序列的GenBank登录号为BankIt1712036 GeneMark.hmm KJ624918。
