Yang Jingsi, Xu Bingshuang, Gao Zengqiang, Zhou Ke, Liu Peng, Dong Yuhui, Zhang Jianjun, Liu Quansheng
College of Chemistry, Dalian University of Technology, 2 Linggong Road, Ganjingzi District, Dalian 116024, People's Republic of China.
Multi-Discipline Research Center, Institute of High Energy Physics, Chinese Academy of Sciences, Yuquan Road 19B, Beijing 100049, People's Republic of China.
Acta Crystallogr F Struct Biol Commun. 2017 Sep 1;73(Pt 9):505-510. doi: 10.1107/S2053230X17011529. Epub 2017 Aug 14.
Toxin-antitoxin (TA) systems are widespread in both bacteria and archaea, where they enable cells to adapt to environmental cues. TA systems play crucial roles in various cellular processes, such as programmed cell death, cell growth, persistence and virulence. Here, two distinct forms of the type II toxin-antitoxin complex HicAB were identified and characterized in Escherichia coli K-12, and both were successfully overexpressed and purified. The two proposed forms, HicAB and HicAB, differed in the presence or absence of a seven-amino-acid segment at the N-terminus in the antitoxin HicB. The short form HicAB readily crystallized under the conditions 0.1 M Tris-HCl pH 8.0, 20%(w/v) PEG 6000, 0.2 M ammonium sulfate. The HicAB crystal diffracted and data were collected to 2.5 Å resolution. The crystal belonged to space group I222 or I222, with unit-cell parameters a = 67.04, b = 66.31, c = 120.78 Å. Matthews coefficient calculation suggested the presence of two molecules each of HicA and HicB in the asymmetric unit, with a solvent content of 55.28% and a Matthews coefficient (V) of 2.75 Å Da.
毒素-抗毒素（TA）系统广泛存在于细菌和古生菌中，使细胞能够适应环境信号。TA系统在各种细胞过程中发挥关键作用，如程序性细胞死亡、细胞生长、持留性和毒力。在此，在大肠杆菌K-12中鉴定并表征了两种不同形式的II型毒素-抗毒素复合物HicAB，且二者均成功实现了过表达和纯化。所提出的两种形式，即HicAB和HicAB，在抗毒素HicB的N端是否存在一个七氨基酸片段上存在差异。短形式的HicAB在0.1 M Tris-HCl pH 8.0、20%（w/v）PEG 6000、0.2 M硫酸铵的条件下易于结晶。HicAB晶体产生衍射，数据收集至2.5 Å分辨率。该晶体属于空间群I222或I222，晶胞参数a = 67.04、b = 66.31、c = 120.78 Å。马修斯系数计算表明，不对称单元中每个HicA和HicB各有两个分子，溶剂含量为55.28%，马修斯系数（V）为2.75 Å Da。
