Larson Steven B, Day John S, Nguyen Chieugiang, Cudney Robert, McPherson Alexander
Department of Molecular Biology and Biochemistry, The University of California, Irvine, 92697-3900, USA.
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2009 Mar 1;65(Pt 3):192-8. doi: 10.1107/S1744309109002218. Epub 2009 Feb 12.
Proteinase K, a subtilisin-like fungal protease, was crystallized from a cocktail of small molecules containing digalacturonic acid (DGA). The crystal structure was determined to 1.32 A resolution and refined to an R factor of 0.158. The final model contained, beside the protein, two calcium ions, 379 water molecules, a molecule of DGA and a partially occupied HEPES molecule. The DGA molecule has one sugar moiety disposed exactly on a crystallographic twofold axis; the second ring was not observed. The DGA molecule is bound to two protein molecules across the twofold axis through hydrogen-bonding networks involving Ser150 and water molecules. One of the calcium-ion sites has not been reported previously. This study further illustrates the involvement of small molecules in the crystallization of macromolecules through their ability to form intermolecular lattice interactions.
蛋白酶K是一种枯草杆菌蛋白酶样真菌蛋白酶，它是从含有二半乳糖醛酸（DGA）的小分子混合物中结晶得到的。晶体结构的分辨率为1.32埃，并精修至R因子为0.158。最终模型除蛋白质外，还包含两个钙离子、379个水分子、一个DGA分子和一个部分占据的HEPES分子。DGA分子的一个糖部分正好位于晶体学二重轴上；未观察到第二个环。DGA分子通过涉及Ser150和水分子的氢键网络，在二重轴上与两个蛋白质分子结合。其中一个钙离子位点以前尚未有报道。这项研究进一步说明了小分子通过其形成分子间晶格相互作用的能力参与大分子的结晶过程。
