3-DIMENSIONAL STRUCTURE OF BETA-GALACTOSIDASE FROM ESCHERICHIA-COLI
3-DIMENSIONAL STRUCTURE OF BETA-GALACTOSIDASE FROM ESCHERICHIA-COLI
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DOI：
10.1038/369761a0
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发表时间：
1994-06-30
期刊：
影响因子：
64.8
通讯作者：
MATTHEWS, BW
中科院分区：
文献类型：
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作者：
JACOBSON, RH;ZHANG, XJ;MATTHEWS, BW
大肠杆菌中的β-半乳糖苷酶在操纵子模型的发展中起了重要作用，如今它是分子生物学中最常用的酶之一。在这里，我们报告这种蛋白质的结构，并表明它是一个四聚体与222点对称性。1，023个氨基酸的多肽链（2，3）折叠成五个连续的结构域，在氨基末端有一个延伸段。该氨基末端片段参与亚基界面，再加上观察到每个活性位点由来自两个不同亚基的元素组成，为α互补现象提供了结构上的基本原理。该结构代表已确定原子结构的最长多肽链。我们的研究结果表明，它是可能成功地研究非病毒蛋白质晶体的晶胞尺寸超过500埃，相对分子质量在2,000 K/不对称单位的区域。非晶体学对称性平均被证明是结构确定中非常强大的工具，正如在其他背景下所示的那样（31，32）。
THE beta-galactosidase from Escherichia coli was instrumental in the development of the operon model(1), and today is one of the most commonly used enzymes in molecular biology. Here we report the structure of this protein and show that it is a tetramer with 222- point symmetry. The 1,023-amino-acid polypeptide chain(2,3) folds into five sequential domains, with an extended segment at the amino terminus. The participation of this amino-terminal segment in a subunit interface, coupled with the observation that each active site is made up of elements from two different subunits, provides a structural rationale for the phenomenon of alpha-complementation. The structure represents the longest polypeptide chain for which an atomic structure has been determined. Our results show that it is possible successfully to study non-viral protein crystals with unit cell dimensions in excess of 500 Angstrom and with relative molecular masses in the region of 2,000K per asymmetric unit. Non-crystallographic symmetry averaging proved to be a very powerful tool in the structure determination, as has been shown in other contexts(31,32).