Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
Acta Crystallogr F Struct Biol Commun. 2020 Sep 1;76(Pt 9):398-405. doi: 10.1107/S2053230X20010572. Epub 2020 Aug 20.
During the crystal structure analysis of an ATP-binding cassette (ABC) transporter overexpressed in Escherichia coli, a contaminant protein was crystallized. The identity of the contaminant was revealed by mass spectrometry to be the Escherichia coli transcription terminator factor Rho, structures of which had been previously determined in different conformational states. Although Rho was present at only ∼1% of the target protein (a bacterial homolog of the eukaryotic ABC transporter of mitochondria from Novosphingobium aromaticivorans; NaAtm1), it preferentially crystallized in space group C2 as thin plates that diffracted to 3.30 Å resolution. The structure of Rho in this crystal form exhibits a hexameric open-ring staircase conformation with bound ATP; this characteristic structure was also observed on electron-microscopy grids of the NaAtm1 preparation.
在对大肠杆菌中过表达的 ATP 结合盒（ABC）转运蛋白进行晶体结构分析时，发现了一种污染物蛋白。通过质谱分析揭示，该污染物蛋白是大肠杆菌转录终止因子 Rho，此前已在不同构象状态下对其结构进行了测定。尽管 Rho 仅占靶蛋白（Novosphingobium aromaticivorans 中的真核 ABC 转运蛋白的细菌同源物 NaAtm1）的约 1%，但它优先以 C2 空间群作为薄片形式结晶，可衍射至 3.30 Å 的分辨率。这种晶体形式的 Rho 结构呈现出具有结合 ATP 的六聚体开环梯级构象；在 NaAtm1 制剂的电子显微镜网格上也观察到了这种特征结构。
