Havukainen R, Törrönen A, Laitinen T, Rouvinen J
Department of Chemistry, University of Joensuu, Finland.
Biochemistry. 1996 Jul 23;35(29):9617-24. doi: 10.1021/bi953052n.
The three-dimensional structures of endo-1,4-xylanase II (XYNII) from Trichoderma reesei complexed with 4,5-epoxypentyl beta-D-xyloside (X-O-C5),3,4-epoxybutyl beta-D-xyloside (X-O-C4), and 2,3-epoxypropyl beta-D-xyloside (X-O-C3) were determined by X-ray crystallography. High-resolution measurement revealed clear electron densities for each ligand. Both X-O-C5 and X-O-C3 were found to form a covalent bond with the putative nucleophile Glu86. Unexpectedly, X-O-C4 was found to bind to the putative acid/base catalyst Glu177. In all three complexes, clear conformational changes were found in XYNII compared to the native structure. These changes were largest in the X-O-C3 complex structure.
通过X射线晶体学确定了里氏木霉内切-1,4-木聚糖酶II（XYNII）与4,5-环氧戊基β-D-木糖苷（X-O-C5）、3,4-环氧丁基β-D-木糖苷（X-O-C4）和2,3-环氧丙基β-D-木糖苷（X-O-C3）复合后的三维结构。高分辨率测量揭示了每个配体清晰的电子密度。发现X-O-C5和X-O-C3均与推定的亲核试剂Glu86形成共价键。出乎意料的是，发现X-O-C4与推定的酸碱催化剂Glu177结合。在所有三种复合物中，与天然结构相比，XYNII中均发现了明显的构象变化。这些变化在X-O-C3复合结构中最大。
