Tsukada H, Blow D M
J Mol Biol. 1985 Aug 20;184(4):703-11. doi: 10.1016/0022-2836(85)90314-6.
Diffraction data for alpha-chymotrypsin crystals at -10 degrees C were measured at 1.68 A resolution and refined by restrained structure-factor least-squares refinement. The two independent chymotrypsin molecules in the crystallographic asymmetric unit were refined independently. The overall structure of alpha-chymotrypsin is little changed from published co-ordinates. The root-mean-square shift of C alpha co-ordinates is 0.42 A, co-ordinates for the two molecules showing a root-mean-square difference of 0.19 A. Certain regions with high disorder (residues 9 to 14, 73 to 79) remain difficult to interpret and several side-chains are disordered. Some water molecule positions have been changed. The absence of the tosyl group has made a significant difference to the refined structure at the active site. This now agrees closely with other enzymes of the trypsin family that have been refined at high resolution. There is a strong hydrogen bond between N epsilon 2 (His57) and O gamma (Ser195) in the free enzyme, in line with the published description of the charge relay system.
在-10℃下对α-糜蛋白酶晶体的衍射数据进行了测量，分辨率为1.68 Å，并通过结构因子约束最小二乘法进行了精修。晶体学不对称单元中的两个独立糜蛋白酶分子分别进行了精修。α-糜蛋白酶的整体结构与已发表的坐标相比变化不大。Cα坐标的均方根位移为0.42 Å，两个分子的坐标显示均方根差异为0.19 Å。某些高度无序的区域（残基9至14、73至79）仍然难以解释，并且几个侧链是无序的。一些水分子的位置发生了变化。甲苯磺酰基的缺失对活性位点的精修结构产生了显著影响。现在它与已在高分辨率下精修的胰蛋白酶家族的其他酶非常吻合。在游离酶中，Nε2（His57）和Oγ（Ser195）之间存在很强的氢键，这与电荷中继系统的已发表描述一致。
