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Biochemical Properties and Biological Function of a Monofunctional Microbial Biotin Protein Ligase

机译：单功能微生物生物素蛋白连接酶的生化特性和生物学功能

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摘要

Biotin protein ligases constitute a family of enzymes that catalyze the linkage of biotin to biotin-ndependent carboxylases. In bacteria, these enzymes are functionally divided into two classes: the monofunc-ntional enzymes that catalyze only biotin addition and the bifunctional enzymes that also bind to DNA tonregulate transcription initiation. Biochemical and biophysical studies of the bifunctional Escherichia colinligase suggest that several properties of the enzyme have evolved to support its additional regulatory role.nIncluded among these properties are the order of substrate binding and linkage between the oligomeric statenand ligand binding. To test this hypothesized relationship between functionality and biochemical properties innligases, we have conducted studies of the monofunctional ligase from Pyrococcus horikoshii. Sedimentationnequilibrium measurements to determine the effect of ligand binding on oligomerization indicate that thenenzyme exists as a dimer regardless of liganded state. Measurements performed using isothermal titrationncalorimetry and fluorescence spectroscopy indicate that, in contrast to the bifunctional E. coli enzyme,nsubstrate binding does not occur by an obligatorily ordered mechanism. Finally, thermodynamic signaturesnof ligand binding to the monofunctional enzyme differ significantly from those measured for the bifunctionalnenzyme. These results indicate a correlation between the functional complexity of biotin protein ligases andntheir detailed biochemical characteristics.
机译：生物素蛋白连接酶构成一族酶，催化生物素与生物素非依赖性羧化酶的连接。在细菌中，这些酶在功能上分为两类：仅催化生物素添加的单功能酶和还与DNA结合的双功能酶可调节转录起始。对双功能大肠杆菌colinligase的生化和生物物理研究表明，该酶的几种特性已经发展以支持其额外的调节作用。这些特性包括底物结合的顺序以及寡聚状态蛋白与配体结合之间的连接。为了测试功能性和生化特性连接酶之间的这种假设关系，我们进行了火球菌单功能连接酶的研究。沉淀平衡测定法测定配体结合对低聚的影响表明，无论配体状态如何，酶均以二聚体形式存在。使用等温滴定量热法和荧光光谱法进行的测量表明，与双功能大肠杆菌酶相反，通过强制性排序机制不会发生n底物结合。最后，配体与单功能酶结合的热力学特征与双功能酶的热特征明显不同。这些结果表明生物素蛋白连接酶的功能复杂性与其详细的生化特征之间的相关性。

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  • 来源
    《Biochemistry》 |2010年第25期|p.5358-5365|共8页
  • 作者

    Kyle G. Daniels and Dorothy Beckett;

  • 作者单位

    Department of Chemistry and Biochemistry, Center for Biological Structure and Organization, University of Maryland,College Park, Maryland 20742;

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