您当前所在位置: 首页 > 学者

郑晓峰

  • 21浏览

  • 0点赞

  • 0收藏

  • 0分享

  • 60下载

  • 0评论

  • 引用

期刊论文

Alternative IMP Binding in Feedback Inhibition of Hypoxanthine-Guanine Phosphoribosyltransferase from Thermoanaerobacter tengcongensis

郑晓峰Qiang Chen Yuhe Liang Xiaodong Su Xiaocheng Gu Xiaofeng Zheng and Ming Luo *

J. Mol. Biol. (2005) 348, 1199-1210,-0001,():

URL:

摘要/描述

Crystal structures of Thermoanaerobacter tengcongensis hypoxanthine-guanine phosphoribosyltransferase (HGPRT) apoenzyme and the enzyme–inosine monophosphate (IMP) complex have been determined to 2.5A ° and 2.2A ° resolution, respectively. The active form of the enzyme was identified as a tetramer in solution and the Ki value of IMP was measured to be 45 mM for a-D-phosphoribosyl-1-pyrophosphate (PRPP). Conformation of the flexible loop in T. tengcongensis HGPRT, which is involved in substrate PRPP binding, is different from that observed in phosphoribosyltransferases (PRTs). It contains a 3-10 helix, and a unique double serine repeat. This loop is ordered even in the apoenzyme and assumes a half-closed conformation. The primary magnesium ion is directly coordinated by side-chains of Glu101 and Asp102, and water molecules in the apoenzyme, suggesting a possible prerequisite role for substrate PRPP binding. Most interestingly, an alternative IMP binding mode is found in the structure of T. tengcongensis HGPRT-IMP complex. The 50-phosphate of IMP occupies the PPi position usually seen in PRT-PRPP complexes. This new observation is consistent with the lower Ki value of IMP and may suggest a mechanism involving multiple modes of interactions between IMP and T. tengcongensis HGPRT in product release and feedback inhibition. The structure of T. tengcongensis HGPRT is compared with those of mesophilic HPRTs, and several possible features contributing to its thermostability are elucidated. Overall, T. tengcongensis HGPRT appears to be more diverged from other PRTs.

【免责声明】以下全部内容由[郑晓峰]上传于[2010年10月28日 10时52分56秒],版权归原创者所有。本文仅代表作者本人观点,与本网站无关。本网站对文中陈述、观点判断保持中立,不对所包含内容的准确性、可靠性或完整性提供任何明示或暗示的保证。请读者仅作参考,并请自行承担全部责任。

我要评论

全部评论 0

本学者其他成果

    同领域成果