ESCHERICHIA-COLI BIOTIN HOLOENZYME SYNTHETASE BIOREPRESSOR CRYSTAL-STRUCTURE DELINEATES THE BIOTIN-BINDING AND DNA-BINDING DOMAINS
ESCHERICHIA-COLI BIOTIN HOLOENZYME SYNTHETASE BIOREPRESSOR CRYSTAL-STRUCTURE DELINEATES THE BIOTIN-BINDING AND DNA-BINDING DOMAINS
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DOI：
10.1073/pnas.89.19.9257
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发表时间：
1992-10-01
影响因子：
11.1
通讯作者：
MATTHEWS, BW
中科院分区：
文献类型：
--
作者：
WILSON, KP;SHEWCHUK, LM;MATTHEWS, BW
的三维结构的BirA，大肠杆菌生物素生物合成操纵子的阻遏物，已被确定通过X射线晶体学和细化到19.0%的晶体学残留在2.3埃的分辨率。BirA是一种序列特异性DNA结合蛋白，也催化生物素和ATP形成生物素基-5 '-腺苷酸，并将生物素部分转移至其他蛋白质。细胞中生物素生物合成酶的水平由生物素基-5 '-腺苷酸的量控制，生物素基-5'-腺苷酸是BirA辅阻遏物。该结构提供了一个转录因子也是一种酶的例子。BirA的结构是高度不对称的，由三个结构域组成。N-末端结构域主要是α-螺旋，含有螺旋-转角-螺旋DNA结合基序，并且与分子的其余部分松散连接。中心结构域由七链混合β-折叠组成，其中α-螺旋覆盖一面。片材的另一面大部分暴露于溶剂中并含有活性部位。C-末端结构域包含六链、反向平行的β-折叠夹层。生物素结合的位置与影响酶活性的突变一致。附近的环具有与其他蛋白质中的磷酸盐结合相关的序列。据推断，ATP结合在该区域，与生物素相邻。有人提出辅阻遏物与单体BirA的结合可能通过促进多聚体BirA-辅阻遏物-DNA复合物的形成来促进DNA结合。然而，这个复杂的结构细节仍然是一个悬而未决的问题。
The three-dimensional structure of BirA, the repressor of the Escherichia coli biotin biosynthetic operon, has been determined by x-ray crystallography and refined to a crystallographic residual of 19.0% at 2.3-angstrom resolution. BirA is a sequence-specific DNA-binding protein that also catalyzes the formation of biotinyl-5'-adenylate from biotin and ATP and transfers the biotin moiety to other proteins. The level of biotin biosynthetic enzymes in the cell is controlled by the amount of biotinyl-5'-adenylate, which is the BirA corepressor. The structure provides an example of a transcription factor that is also an enzyme. The structure of BirA is highly asymmetric and consists of three domains. The N-terminal domain is mostly alpha-helical, contains a helix-turn-helix DNA-binding motif, and is loosely connected to the remainder of the molecule. The central domain consists of a seven-stranded mixed beta-sheet with alpha-helices covering one face. The other side of the sheet is largely solvent-exposed and contains the active site. The C-terminal domain comprises a six-stranded, antiparallel beta-sheet sandwich. The location of biotin binding is consistent with mutations that affect enzymatic activity. A nearby loop has a sequence that has been associated with phosphate binding in other proteins. It is inferred that ATP binds in this region, adjacent to the biotin. It is proposed that the binding of corepressor to monomeric BirA may promote DNA binding by facilitating the formation of a multimeric BirA-corepressor-DNA complex. The structural details of this complex remain an open question, however.