標題: Roles of Amino Acids in the Escherichia coli Octaprenyl Diphosphate Synthase Active Site Probed by Structure-Guided Site-Directed Mutagenesis
作者: Chang, Keng-Ming
Chen, Shih-Hsun
Kuo, Chih-Jung
Chang, Chi-Kang
Guo, Rey-Ting
Yang, Jinn-Moon
Liang, Po-Huang
生物科技學系
Department of Biological Science and Technology
公開日期: 24-四月-2012
摘要: Octaprenyl diphosphate synthase (OPPS) catalyzes consecutive condensation reactions of farnesyl diphosphate (FPP) with five molecules of isopentenyl diphosphates (IPP) to generate C-40 octaprenyl diphosphate, which constitutes the side chain of ubiquinone or menaquinone. To understand the roles of active site amino acids in substrate binding and catalysis, we conducted site-directed mutagenesis studies with Escherichia coli OPPS. In conclusion, D85 is the most important residue in the first DDXXD motif for both FPP and IPP binding through an H-bond network involving R93 and R94, respectively, whereas R94, K45, R48, and H77 are responsible for IPP binding by providing H-bonds and ionic interactions. K170 and T171 may stabilize the farnesyl carbocation intermediate to facilitate the reaction, whereas R93 and K225 may stabilize the catalytic base (MgPPi) for H-R proton abstraction after IPP condensation. K225 and K235 in a flexible loop may interact with FPP when the enzyme becomes a closed conformation, which is therefore crucial for catalysis. Q208 is near the hydrophobic part of IPP and is important for IPP binding and catalysis.
URI: http://hdl.handle.net/11536/16023
ISSN: 0006-2960
期刊: BIOCHEMISTRY
Volume: 51
Issue: 16
結束頁: 3412
顯示於類別:期刊論文


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