Gurmu Daniel, Dahlroth Sue-Li, Haas Juergen, Nordlund Pär, Erlandsen Heidi
Medical Biochemistry and Biophysics, Karolinska Institutet, Scheeles Väg 2, SE-171 77 Stockholm, Sweden.
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2010 Jun 1;66(Pt 6):734-7. doi: 10.1107/S1744309110016052. Epub 2010 May 29.
Ribonucleotide reductase (RNR) is responsible for converting ribonucleotides to deoxyribonucleotides, which are the building blocks of DNA. The enzyme is present in all life forms as well as in some large DNA viruses such as herpesviruses. The alpha-herpesviruses and gamma-herpesviruses encode two class Ia RNR subunits, R1 and R2, while the beta-herpesvirus subfamily only encode an inactive R1 subunit. Here, the crystallization of the R2 subunit of RNR encoded by the ORF60 gene from the oncovirus Kaposi's sarcoma-associated gamma-herpesvirus (KSHV) is reported. These are the first crystals of a viral R2 subunit; the use of in situ proteolysis with chymotrypsin and the addition of hexamine cobalt(III) chloride that were necessary to obtain crystals are described. Optimization of the crystallization conditions yielded crystals that diffracted to 2.0 A resolution. The crystals belonged to space group P2(1), with unit-cell parameters a = 63.9, b = 71.2, c = 71.8 A, alpha = 90, beta = 106.7, gamma = 90 degrees. The data set collected was 95.3% complete, with an R(merge) of 9.6%. There are two molecules in the asymmetric unit, corresponding to a solvent content of 43.4%.
核糖核苷酸还原酶（RNR）负责将核糖核苷酸转化为脱氧核糖核苷酸，而脱氧核糖核苷酸是DNA的组成成分。这种酶存在于所有生命形式以及一些大型DNA病毒（如疱疹病毒）中。α-疱疹病毒和γ-疱疹病毒编码两种Ia类RNR亚基，即R1和R2，而β-疱疹病毒亚科仅编码一种无活性的R1亚基。在此，报道了肿瘤病毒卡波西肉瘤相关γ-疱疹病毒（KSHV）的ORF60基因编码的RNR的R2亚基的结晶情况。这些是病毒R2亚基的首批晶体；描述了使用胰凝乳蛋白酶进行原位蛋白水解以及添加六氨合钴（III）氯化物以获得晶体的必要性。结晶条件的优化产生了衍射分辨率达到2.0 Å的晶体。这些晶体属于空间群P2(1)，晶胞参数为a = 63.9、b = 71.2、c = 71.8 Å，α = 90°、β = 106.7°、γ = 90°。收集到的数据集完整性为95.3%，合并R值（R(merge)）为9.6%。不对称单元中有两个分子，溶剂含量为43.4%。
