STRUCTURAL CHARACTERIZATION AND COREPRESSOR BINDING OF THE ESCHERICHIA-COLI PURINE REPRESSOR
STRUCTURAL CHARACTERIZATION AND COREPRESSOR BINDING OF THE ESCHERICHIA-COLI PURINE REPRESSOR
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DOI：
10.1128/jb.174.19.6207-6214.1992
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发表时间：
1992-10-01
影响因子：
3.2
通讯作者：
ZALKIN, H
中科院分区：
文献类型：
--
作者：
CHOI, KY;ZALKIN, H
大肠杆菌嘌呤抑制因子PurR与一个16bp的操作符序列结合，并协同调节嘌呤和嘧啶核苷酸的重新合成、生物合成的单碳单元的形成和胞嘧啶的脱胺化。我们已经对纯化的抑制因子进行了表征。化学交联表明PurR是二聚体。每个亚基有一个包含52个氨基酸的n端结构域用于DNA结合，一个包含289个氨基酸的c端结构域用于辅抑制因子结合。每个结构域经胰蛋白酶裂解后分离得到。二聚体形成的位点存在于辅抑制子结合区域内。次黄嘌呤和鸟嘌呤协同结合到每个亚基的不同位点。竞争实验表明，一个嘌呤的结合消除了协同性，降低了第二个辅抑制因子的亲和力和结合。通过三个色氨酸残基的固有荧光检测，每个辅抑制子的结合导致辅抑制子结合域的构象变化。这些实验表明PurR是一种复杂的变构调节蛋白。
The Escherichia coli purine repressor, PurR, binds to a 16-bp operator sequence and coregulates the genes for de novo synthesis of purine and pyrimidine nucleotides, formation of a one-carbon unit for biosynthesis, and deamination of cytosine. We have characterized the purified repressor. Chemical cross-linking indicates that PurR is dimeric. Each subunit has an N-terminal domain of 52 amino acids for DNA binding and a C-terminal 289-residue domain for corepressor binding. Each domain was isolated after cleavage by trypsin. Sites for dimer formation are present within the corepressor binding domain. The corepressors hypoxanthine and guanine bind cooperatively to distinct sites in each subunit. Competition experiments indicate that binding of one purine abolishes cooperativity and decreases the affinity and the binding of the second corepressor. Binding of each corepressor results in a conformation change in the corepressor binding domain that was detected by intrinsic fluorescence of three tryptophan residues. These experiments characterize PurR as a complex allosteric regulatory protein.