A Conserved Aspartate of tRNA Pseudouridine Synthase Is Essential for Activity and a Probable Nucleophilic Catalyst

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• 作者：Lixuan Huang ; Manee Pookanjanatavip ; Xiangrong Gu ; and Daniel V. Santi
• 刊名：Biochemistry
• 出版年：1998
• 出版时间：January 6, 1998
• 年：1998
• 卷：37
• 期：1
• 页码：344 - 351
• 全文大小：317K
• 年卷期：v.37,no.1(January 6, 1998)
• ISSN：1520-4995

文摘

tRNA pseudouridine synthase I catalyzes the conversion of uridineto pseudouridine at positions38, 39, and/or 40 in the anticodon loop of many tRNAs.Pseudouridine synthase I was cloned behind aT7 promoter and expressed in Escherichia coli to about 20%of total soluble proteins. Fluorouracil-substituted tRNA caused a time-dependent inactivation of pseudouridinesynthase I and formed a covalentcomplex with the enzyme that involved the FUMP at position 39.Asp60, conserved in all known andputative pseudouridine synthases, was mutated to amino acids withdiverse side chains. All Asp60 mutantsbound tRNA but were catalytically inactive and failed to form covalentcomplexes with fluorouracil-substituted tRNA. We conclude that the conserved Asp60 is essentialfor pseudouridine synthase activityand propose mechanisms which involve this residue in importantcatalytic roles.