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首页> 外文期刊>Biochemistry >Crystal Structure of S-Ribosylhomocysteinase(LuxS)in Complex with a Catalytic 2-Ketone Intermediate
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Crystal Structure of S-Ribosylhomocysteinase(LuxS)in Complex with a Catalytic 2-Ketone Intermediate

机译：S-核糖基同型半胱氨酸酶（LuxS）在催化2-酮中间体的配合物中的晶体结构

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摘要

S-Ribosylhomocysteinase(LuxS)is an Fe~(2+)-dependent metalloenzyme that catalyzes the cleavage of the thioether bond in S-ribosylhomocysteine(SRH)to produce homocysteine(Hcys)and 4,5-dihydroxy-2,3-pentanedione(DPD),the precursor of type II bacterial quorum-sensing molecule.The proposed mechanism involves an initial metal-catalyzed aldose-ketose isomerization reaction,which results in the migration of the ribose carbonyl group from its C1 to C2 position and the formation of a 2-ketone intermediate.A repetition of the isomerization reaction shifts the carbonyl group to the C3 position.Subsequent beta-elimination reaction at the C4 and C5 positions completes the catalytic cycle.In this work,a catalytically inactive mutant(C84A)of Co~(2+)-substituted Bacillus subtilis LuxS was cocrystallized with the 2-ketone intermediate and the structure was determined to 1.8 A resolution.The structure reveals that the C2 carbonyl oxygen is directly coordinated with the metal ion,providing strong support for the proposed Lewis acid function of the metal ion during catalysis.Cys-84 and Glu-57 are optimally positioned to act as general acids/bases during the isomerization and elimination reactions.In addition,Ser-6,His-11,and Arg-39 are involved in substrate/ intermediate binding through hydrogen bonding interactions.The above conclusions are further confirmed by site-directed mutagenesis and visible absorption spectroscopic studies.
机译：S-核糖基同型半胱氨酸酶（LuxS）是一种Fe〜（2+）依赖性金属酶，催化S-核糖基同型半胱氨酸（SRH）中硫醚键的裂解，生成高半胱氨酸（Hcys）和4,5-二羟基-2,3-戊二酮（DPD）是II型细菌群体感应分子的前体。拟议的机理涉及初始的金属催化的醛糖-酮糖异构化反应，该反应导致核糖羰基从其C1迁移至C2位置并形成核糖基。异构化反应的重复将羰基转移到C3位置，随后在C4和C5位置进行β消除反应完成了催化循环。在这项工作中，Co的无催化活性的突变体（C84A）将〜（2+）取代的枯草芽孢杆菌LuxS与2-酮中间体共结晶，确定结构至1.8 A拆分。该结构表明C2羰基氧与金属离子直接配位，提供了强支撑拟议中的金属离子的路易斯酸功能.Cys-84和Glu-57处于最佳位置，可在异构化和消除反应中充当一般酸/碱。此外，Ser-6，His-11和Arg -39通过氢键相互作用参与底物/中间体的结合。上述结论通过定点诱变和可见吸收光谱研究得到了进一步证实。

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