Afamin, which is a human blood plasma glycoprotein, a putative multifunctional transporter of hydrophobic molecules and a marker for metabolic syndrome, poses multiple challenges for crystallographic structure determination, both practically and in analysis of the models. Several hundred crystals were analysed, and an unusual variability in cell volume and difficulty in solving the structure despite an ∼34% sequence identity with nonglycosylated human serum albumin indicated that the molecule exhibits variable and context-sensitive packing, despite the simplified glycosylation in insect cell-expressed recombinant afamin. Controlled dehydration of the crystals was able to stabilize the orthorhombic crystal form, reducing the number of molecules in the asymmetric unit from the monoclinic form and changing the conformational state of the protein. An iterative strategy using fully automatic experiments available on MASSIF-1 was used to quickly determine the optimal protocol to achieve the phase transition, which should be readily applicable to many types of sample. The study also highlights the drawback of using a single crystallographic structure model for computational modelling purposes given that the conformational state of the binding sites and the electron density in the binding site, which is likely to result from PEGs, greatly varies between models. This also holds for the analysis of nonspecific low-affinity ligands, where often a variety of fragments with similar uncertainty can be modelled, inviting interpretative bias. As a promiscuous transporter, afamin also seems to bind gadoteridol, a magnetic resonance imaging contrast compound, in at least two sites. One pair of gadoteridol molecules is located near the human albumin Sudlow site, and a second gadoteridol molecule is located at an intermolecular site in proximity to domain IA. The data from the co-crystals support modern metrics of data quality in the context of the information that can be gleaned from data sets that would be abandoned on classical measures.

中文翻译：

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受控的脱水，结构柔韧性和g MRI对比了人血浆糖蛋白afamin中的化合物结合。

Afamin是一种人血浆糖蛋白，是疏水分子的多功能转运蛋白和代谢综合征的标志物，在晶体结构确定和实际分析中都面临着多重挑战。分析了数百个晶体，尽管与非糖基化的人血清白蛋白有约34％的序列同一性，但是细胞体积的异常可变性和解决结构的困难性表明，尽管昆虫细胞中的糖基化简化，但该分子仍表现出可变的和上下文相关的堆积表达的重组Afamin。晶体的受控脱水能够稳定正交晶体的形式，从单斜晶形式减少不对称单元中的分子数目，并改变蛋白质的构象状态。使用在MASSIF-1上可用的全自动实验的迭代策略来快速确定实现相变的最佳方案，该相变应易于适用于多种类型的样品。该研究还突出了使用单一晶体结构模型进行计算建模的缺点，因为模型之间的结合位点的构象状态和结合位点中的电子密度（可能由PEG引起）存在很大差异。这也适用于非特异性低亲和力配体的分析，通常可以对具有相似不确定性的各种片段进行建模，从而引起解释偏见。作为混杂的转运蛋白，afamin似乎也至少在两个部位结合了gadoteridol（一种磁共振成像造影剂）。一对gadoteridol分子位于人白蛋白Sudlow位点附近，第二个gadoteridol分子位于域IA附近的分子间位点。从共晶体中获得的数据可以在可以从经典测量中遗弃的数据集中收集到的信息中支持现代数据质量指标。