Dao-Thi M H, Wyns L, Poortmans F, Bahassi E M, Couturier M, Loris R
Laboratorium voor Ultrastructuur, Vlaams Interuniversitair Instituut Biotechnologie, Vrije Universiteit Brussel, Paardenstraat 65, B-1640 Sint-Genesius-Rode, Belgium.
Acta Crystallogr D Biol Crystallogr. 1998 Sep 1;54(Pt 5):975-81. doi: 10.1107/s0907444997011554.
CcdB is a small dimeric protein that poisons DNA-topoisomerase II complexes. Its crystallization properties in terms of precipitant type, precipitant concentration, pH and protein concentration have been investigated leading to a novel crystal form which, in contrast to previously reported crystals, is suitable for structure determination using the multiple isomorphous replacement (MIR) method. The space group of this new form is C2, with unit-cell parameters a = 74.94, b = 36.24, c = 35.77 A, beta = 115.27 degrees. The asymmetric unit contains a single monomer. Flash-frozen crystals diffract to at least 1.5 A resolution, while room-temperature diffraction can be observed up to 1.6 A. The double mutant S74C/G77Q, which acts as a super-killer, crystallizes in space group I222 (or I212121) with unit-cell dimensions a = 105.58, b = 105.80, c = 91.90 A. These crystals diffract to 2.5 A resolution.
CcdB是一种小型二聚体蛋白，可毒害DNA拓扑异构酶II复合物。已研究了其在沉淀剂类型、沉淀剂浓度、pH值和蛋白质浓度方面的结晶特性，从而得到了一种新型晶体形式，与先前报道的晶体不同，这种晶体形式适用于使用多重同晶置换（MIR）方法进行结构测定。这种新形式的空间群为C2，晶胞参数为a = 74.94、b = 36.24、c = 35.77 Å，β = 115.27°。不对称单元包含一个单体。快速冷冻的晶体衍射分辨率至少可达1.5 Å，而室温衍射可观察到1.6 Å。作为超级杀手的双突变体S74C/G77Q在空间群I222（或I212121）中结晶，晶胞尺寸为a = 105.58、b = 105.80、c = 91.90 Å。这些晶体衍射分辨率为2.5 Å。
