SEC-SAXS data from Escherichia coli aspartate transcarbamoylase (ligand-free T-state)

Abstract: E. coli aspartate transcarbamoylase (ATCase) is considered a textbook example of allostery, but the molecular mechanism by which nucleotides exert allosteric control has been long debated. This SEC-SAXS dataset is one of six collected in the presence of different nucleotide conditions at pH 7.5 in the presence of Mg2+. Corresponding cryo-EM map and model: EMD-47956, PDB: 9EEK Experimental description: Size exclusion chromatography (SEC) coupled small-angle X-ray scattering (SAXS) was performed with a 10.0 keV 250 x 250 μm X-ray beam at the Cornell High Energy Synchrotron Source (CHESS) ID7A beamline. The sample (50 μL of 56 μM ATCase in 40 mM Tris-HCl pH 7.5, 15 mM MgCl2, 1 mM TCEP) was centrifuged (15,000 × g, 10 min, 4 °C) and loaded onto a Superdex 200 10/300 GL column (Cytiva) operated by a GE Akta Purifier at 4 °C that was pre-equilibrated in a matched buffer. The elution flowed directly into an in-vacuum X-ray sample cell held at 4 °C at 0.5 mL min−1. Scattering images (2-second exposures) were collected throughout the elution on an Eiger 4M detector covering a range of q ≈ 0.0086 – 0.466 Å−1, where q = 4π/λ sin θ, λ is the X-ray wavelength, and 2θ is the scattering angle. File description: zip file of .dat files integrated in BioXTAS RAW摘要：大肠杆菌天冬氨酸转氨甲酰酶（aspartate transcarbamoylase, ATCase）被视为别构效应（allostery）的经典教科书范例，但核苷酸介导别构调控的分子机制长期以来一直存在学术争议。本SEC-SAXS（Size Exclusion Chromatography coupled Small-Angle X-ray Scattering）数据集是在pH 7.5、Mg²+存在的条件下，于六种不同核苷酸环境中采集的六组数据集之一。对应的冷冻电镜图谱与模型分别为：EMD-47956、PDB: 9EEK。 实验说明：本实验依托康奈尔高能同步辐射光源（Cornell High Energy Synchrotron Source, CHESS）ID7A光束线站，采用10.0 keV、束斑尺寸250×250 μm的X射线完成了尺寸排阻色谱耦合小角X射线散射测试。实验样品为50 μL、浓度56 μM的ATCase溶液，缓冲液体系包含40 mM Tris-HCl（pH 7.5）、15 mM MgCl₂、1 mM 三(2-羧乙基)膦（TCEP）；样品经15,000×g、4℃离心10分钟后，上样至经匹配缓冲液预平衡的Superdex 200 10/300 GL色谱柱（Cytiva公司），色谱分离由GE Akta Purifier系统控制，实验全程维持4℃。色谱洗脱液以0.5 mL·min⁻¹的流速直接流入维持在4℃的真空X射线样品池。实验采用Eiger 4M探测器在洗脱全程收集散射图像，单张图像曝光时长为2秒，探测的散射矢量q范围约为0.0086~0.466 Å⁻¹，其中q=4π/λ sinθ，λ为X射线波长，2θ为散射角。 文件说明：本数据集为经BioXTAS RAW软件积分处理后的.dat格式文件压缩包。