Structure of Tropinone Reductase-II Complexed with NADP+ and Pseudotropine at 1.9 Å Resolution: Implication for Stereospecific Substrate Binding and Catalysis
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- 作者：Atsuko Yamashita ; Hiroaki Kato ; Soichi Wakatsuki ; Takashi Tomizaki ; Toru Nakatsu ; Keiji Nakajima ; Takashi Hashimoto ; Yasuyuki Yamada ; and Jun'ichi Oda
- 刊名：Biochemistry
- 出版年：1999
- 出版时间：June 15, 1999
- 年：1999
- 卷：38
- 期：24
- 页码：7630 - 7637
- 全文大小：233K
- 年卷期：v.38,no.24(June 15, 1999)
- ISSN：1520-4995
文摘
Tropinone reductase-II (TR-II) catalyzes the NADPH-dependent reduction of the carbonylgroup of tropinone to a 
-hydroxyl group. The crystal structure of TR-II complexed with NADP+ andpseudotropine (
-tropine) has been determined at 1.9 Å resolution. A seven-residue peptide near theactive site, disordered in the unliganded structure, is fixed in the ternary complex by participation of thecofactor and substrate binding. The -tropine molecule is bound in an orientation which satisfies theproduct configuration and the stereochemical arrangement toward the cofactor. The substrate binding sitedisplays a complementarity to the bound substrate (-tropine) in its correct orientation. In addition,electrostatic interactions between the substrate and Glu156 seem to specify the binding position andorientation of the substrate. A comparison between the active sites in TR-II and TR-I shows that theyprovide different van der Waals surfaces and electrostatic features. These differences likely contribute tothe correct binding mode of the substrates, which are in opposite orientations in TR-II and TR-I, and todifferent reaction stereospecificities. The active site structure in the TR-II ternary complex also suggeststhat the arrangement of the substrate, cofactor, and catalytic residues is stereoelectronically favorable forthe reaction.
-hydroxyl group. The crystal structure of TR-II complexed with NADP+ andpseudotropine (-tropine) has been determined at 1.9 Å resolution. A seven-residue peptide near theactive site, disordered in the unliganded structure, is fixed in the ternary complex by participation of thecofactor and substrate binding. The -tropine molecule is bound in an orientation which satisfies theproduct configuration and the stereochemical arrangement toward the cofactor. The substrate binding sitedisplays a complementarity to the bound substrate (-tropine) in its correct orientation. In addition,electrostatic interactions between the substrate and Glu156 seem to specify the binding position andorientation of the substrate. A comparison between the active sites in TR-II and TR-I shows that theyprovide different van der Waals surfaces and electrostatic features. These differences likely contribute tothe correct binding mode of the substrates, which are in opposite orientations in TR-II and TR-I, and todifferent reaction stereospecificities. The active site structure in the TR-II ternary complex also suggeststhat the arrangement of the substrate, cofactor, and catalytic residues is stereoelectronically favorable forthe reaction.