Dreusicke D, Schulz G E
Institut für Organische Chemie Freiburg i. Br., F.R.G.
J Mol Biol. 1988 Oct 20;203(4):1021-8. doi: 10.1016/0022-2836(88)90126-x.
Crystalline adenylate kinase from porcine muscle cytosol can assume two interconvertible structures. Here, we report the refined structure of crystal form B at 3.3 A resolution and compare it with crystal form A. Crystal forms A and B can be interconverted by protonation and deprotonation of His36, which is located deep in the active center cleft. The changes concern the molecular packing as well as the polypeptide chain conformation. On conversion from crystal form A to B, the N-terminal alpha-helix unwinds, the active center cleft opens to some extent and the nucleotide-binding glycine-rich loop 15-22 at the active center is detached from the bulk protein. This loop has counterparts in various important mononucleotide-binding proteins and is known to bind a phosphoryl group in adenylate kinase and in the oncogenic ras proteins. It is most likely involved in the phosphoryl transfer and the concomitant conformational changes. it is suggested that the two observed conformations are relevant for enzyme action in solution: they represent two of a series of three known snapshots depicting the enzyme during the substrate binding process.
来自猪肌肉细胞质的结晶腺苷酸激酶可呈现两种可相互转化的结构。在此，我们报告了晶型B在3.3埃分辨率下的优化结构，并将其与晶型A进行比较。晶型A和B可通过位于活性中心裂隙深处的His36的质子化和去质子化相互转化。这些变化涉及分子堆积以及多肽链构象。从晶型A转变为晶型B时，N端α螺旋展开，活性中心裂隙在一定程度上打开，活性中心的富含甘氨酸的核苷酸结合环15 - 22从整体蛋白质上脱离。该环在各种重要的单核苷酸结合蛋白中有对应物，并且已知在腺苷酸激酶和致癌性ras蛋白中结合一个磷酰基。它很可能参与磷酰基转移及伴随的构象变化。有人提出，观察到的这两种构象与溶液中的酶作用相关：它们代表了描绘底物结合过程中该酶的三个已知瞬间中的两个。
