Determination of the structure of alanine racemase from Bacillus stearothermophilus at 1.9-angstrom resolution
Determination of the structure of alanine racemase from Bacillus stearothermophilus at 1.9-angstrom resolution
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DOI：
10.1021/bi961856c
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发表时间：
1997-02-11
期刊：
影响因子：
2.9
通讯作者：
Ringe, D
中科院分区：
文献类型：
--
作者：
Shaw, JP;Petsko, GA;Ringe, D
用X射线晶体学测定了嗜热脂肪芽孢杆菌丙氨酸消旋酶的分子结构，其分辨率为1.9埃。丙氨酸消旋酶单体由两个结构域组成，在N-末端的八链α/β桶，其包括残基1-240，和基本上由β-链（残基241-388）组成的C-末端结构域。在二聚体的结构中，一个单体的α/β桶的口部面对另一个单体的第二结构域。吡哆醛5 '-磷酸（PLP）辅因子位于α/β桶的口部内和口部上方，并通过醛亚胺键与Lys 39共价连接，Lys 39位于α/β桶的第一条β链的C末端。这是PLP辅因子结合在α/β桶的活性位点中的第一个例子。许多其他残基参与维持PLP在蛋白质中的位置。其中，Arg 219是最有趣的，因为它与辅因子的吡啶氮形成氢键。这是第一个已知的发生这样的相互作用与PLP，预计将影响电子离域的PLP-丙氨酸中间体。第二个精氨酸残基Arg 136与PLP的酚氧形成氢键，可能参与底物的结合以及中间体的稳定。最后，来自第二单体的Tyr 265 '被假定为碳负离子中间体的2个质子供体。
The molecular structure of alanine racemase from Bacillus stearothermophilus was determined by X-ray crystallography to a resolution of 1.9 Angstrom. The alanine racemase monomer is composed of two domains, an eight-stranded alpha/beta barrel at the N-terminus, which includes residues 1-240, and a C-terminal domain essentially composed of beta-strand (residues 241-388). In the structure of the dimer the mouth of the alpha/beta barrel of one monomer faces the second domain of the other monomer. The pyridoxal 5'-phosphate (PLP) cofactor lies in and above the mouth of the alpha/beta barrel and is covalently linked via an aldimine linkage to Lys39, which is at the C-terminus of the first beta-strand of the alpha/beta barrel. This is the first example of a PLP cofactor binding in the active site of a alpha/beta barrel. A number of other residues are involved in maintaining the position of the PLP in the protein. Of these, Arg219 is the most interesting, as it forms a hydrogen bond with the pyridine nitrogen of the cofactor. This is the first known occurrence of such an interaction with PLP and is expected to influence the electron delocalization in the PLP-alanine intermediates. A second arginine residue, Arg136, donates a hydrogen bond to the phenolic oxygen of PLP and may be involved in the binding of substrate as well as stabilization of intermediates. Finally, Tyr265', from the second monomer, is postulated to be 2 proton donor to the carbanion intermediate.