Li Mi, Gustchina Alla, Rasulova Fatima S, Melnikov Edward E, Maurizi Michael R, Rotanova Tatyana V, Dauter Zbigniew, Wlodawer Alexander
Protein Structure Section, Macromolecular Crystallography Laboratory, National Cancer Institute at Frederick, Frederick, MD 21702-1201, USA.
Acta Crystallogr D Biol Crystallogr. 2010 Aug;66(Pt 8):865-73. doi: 10.1107/S0907444910019554. Epub 2010 Jul 9.
The structure of a recombinant construct consisting of residues 1-245 of Escherichia coli Lon protease, the prototypical member of the A-type Lon family, is reported. This construct encompasses all or most of the N-terminal domain of the enzyme. The structure was solved by SeMet SAD to 2.6 A resolution utilizing trigonal crystals that contained one molecule in the asymmetric unit. The molecule consists of two compact subdomains and a very long C-terminal alpha-helix. The structure of the first subdomain (residues 1-117), which consists mostly of beta-strands, is similar to that of the shorter fragment previously expressed and crystallized, whereas the second subdomain is almost entirely helical. The fold and spatial relationship of the two subdomains, with the exception of the C-terminal helix, closely resemble the structure of BPP1347, a 203-amino-acid protein of unknown function from Bordetella parapertussis, and more distantly several other proteins. It was not possible to refine the structure to satisfactory convergence; however, since almost all of the Se atoms could be located on the basis of their anomalous scattering the correctness of the overall structure is not in question. The structure reported here was also compared with the structures of the putative substrate-binding domains of several proteins, showing topological similarities that should help in defining the binding sites used by Lon substrates.
报道了由A型Lon家族的典型成员大肠杆菌Lon蛋白酶的1 - 245位残基组成的重组构建体的结构。该构建体包含该酶的全部或大部分N端结构域。利用不对称单元中含有一个分子的三角晶体，通过硒代甲硫氨酸单波长反常散射法将结构解析到2.6埃分辨率。该分子由两个紧密的亚结构域和一个非常长的C端α螺旋组成。第一个亚结构域（1 - 117位残基）主要由β链组成，其结构与先前表达并结晶的较短片段相似，而第二个亚结构域几乎完全是螺旋结构。除了C端螺旋外，两个亚结构域的折叠和空间关系与百日咳博德特氏菌中一个功能未知的203个氨基酸的蛋白质BPP1347的结构非常相似，与其他几种蛋白质的结构关系更远。无法将结构精修到令人满意的收敛程度；然而，由于几乎所有的硒原子都可以基于它们的反常散射定位，所以整体结构的正确性是毋庸置疑的。这里报道的结构还与几种蛋白质的假定底物结合结构域的结构进行了比较，显示出拓扑相似性，这将有助于确定Lon底物使用的结合位点。
