Eads J C, Scapin G, Xu Y, Grubmeyer C, Sacchettini J C
Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461.
Cell. 1994 Jul 29;78(2):325-34. doi: 10.1016/0092-8674(94)90301-8.
The crystal structure of HGPRTase with bound GMP has been determined and refined to 2.5 A resolution. The enzyme has a core alpha/beta structure resembling the nucleotide-binding fold of dehydrogenases, and a second lobe composed of residues from the amino and carboxy termini. The GMP molecule binds in an anti conformation in a solvent-exposed cleft of the enzyme. Lys-165, which forms a hydrogen bond to O6 of GMP, appears to be critical for determining the specificity for guanine and hypoxanthine over adenine. The location of active site residues also provides evidence for a possible mechanism for general base-assisted HGPRTase catalysis. A rationalization of the effects on stability and activity of naturally occurring single amino acid mutations of HGPRTase is presented, including a discussion of several mutations at the active site that lead to Lesch-Nyhan syndrome.
已确定与结合型鸟苷酸一磷酸（GMP）的次黄嘌呤鸟嘌呤磷酸核糖转移酶（HGPRTase）的晶体结构，并将其精修至2.5埃分辨率。该酶具有类似脱氢酶核苷酸结合结构域的核心α/β结构，以及由氨基末端和羧基末端残基组成的第二个叶状结构域。GMP分子以反式构象结合在酶的一个溶剂暴露裂隙中。与GMP的O6形成氢键的赖氨酸-165，似乎对于确定对鸟嘌呤和次黄嘌呤比对腺嘌呤的特异性至关重要。活性位点残基的位置也为一般碱基辅助HGPRTase催化的可能机制提供了证据。本文阐述了对HGPRTase天然存在的单氨基酸突变的稳定性和活性影响的合理化解释，包括对导致莱施-奈恩综合征的活性位点几个突变的讨论。
