Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland.
National Cancer Institute, Argonne, U.S.A.
Acta Biochim Pol. 2021 Jan 24;68(1):29-31. doi: 10.18388/abp.2020_5501.
Protein crystallographers are well aware of the trap of crystallizing E. coli proteins instead of the macromolecule of interest if heterologous recombinant protein expression in E. coli was part of the experimental pipeline. Among the well-known culprits are YodA metal-binding lipocalin (25 kDa) and YadF carbonic anhydrase (a tetramer of 25 kDa subunits). We report a novel crystal form of another such culprit, E. coli HPII catalase, which is a tetrameric protein of ~340 kDa molecular weight. HPII is likely to contaminate recombinant protein samples, co-purify, and then co-crystallize with the target proteins, especially if their masses in size exclusion chromatography are ~300-400 kDa. What makes this case more interesting but also parlous, is the fact that HPII can crystallize from very low concentrations, even well below 1 mg/mL.
蛋白质结晶学家非常清楚，如果大肠杆菌中的异源重组蛋白表达是实验流水线的一部分，那么他们很容易将大肠杆菌蛋白而不是目标大分子结晶出来。其中众所周知的罪魁祸首是 YodA 金属结合脂酰化白蛋白（25kDa）和 YadF 碳酸酐酶（25kDa 亚基的四聚体）。我们报告了另一种此类罪魁祸首，即大肠杆菌 HPII 过氧化氢酶的一种新型晶体形式，它是一种分子量约为 340kDa 的四聚体蛋白。HPII 很可能会污染重组蛋白样品，与靶蛋白共纯化，然后与靶蛋白共结晶，尤其是当它们在排阻色谱中的分子量约为 300-400kDa 时。使这种情况更有趣但也更危险的是，HPII 即使在非常低的浓度下也能结晶，甚至低至 1mg/ml 以下。
