Interferon induced transmembrane proteins (IFITMs) play a dual role in the restriction of RNA viruses and in cancer progression, yet the mechanism of their action remains unknown. Currently, there is no data about the basic biochemical features or biophysical properties of the IFITM1 protein. In this work, we report on description and biochemical characterization of three conformational variants/oligomeric species of recombinant IFITM1 protein derived from an Escherichia coli expression system. The protein was extracted from the membrane fraction, affinity purified, and separated by size exclusion chromatography where two distinct oligomeric species were observed in addition to the expected monomer. These species remained stable upon re-chromatography and were designated as “dimer” and “oligomer” according to their estimated molecular weight. The dimer was found to be less stable compared to the oligomer using circular dichroism thermal denaturation and incubation with a reducing agent. A two-site ELISA and HDX mass spectrometry suggested the existence of structural motif within the N-terminal part of IFITM1 which might be significant in oligomer formation. Together, these data show the unusual propensity of recombinant IFITM1 to naturally assemble into very stable oligomeric species whose study might shed light on IFITM1 anti-viral and pro-oncogenic functions in cells.

中文翻译：

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抗病毒和促转移蛋白 IFITM1 构象变异的生化证据

干扰素诱导跨膜蛋白 (IFITM) 在限制 RNA 病毒和癌症进展中发挥双重作用，但其作用机制仍不清楚。目前，尚无关于IFITM1蛋白的基本生化特征或生物物理特性的数据。在这项工作中，我们报告了来自重组 IFITM1 蛋白的三种构象变体/寡聚体的描述和生化特征。大肠杆菌表达系统。从膜组分中提取蛋白质，进行亲和纯化，并通过尺寸排阻色谱法进行分离，除了预期的单体之外，还观察到两种不同的寡聚体。这些物质在重新色谱分析后保持稳定，并根据其估计的分子量被指定为“二聚体”和“寡聚体”。使用圆二色性热变性和与还原剂孵育，发现二聚体与低聚物相比稳定性较差。双位点 ELISA 和 HDX 质谱分析表明 IFITM1 N 末端部分存在结构基序，这可能对寡聚物的形成具有重要意义。总之，这些数据显示了重组 IFITM1 自然组装成非常稳定的寡聚体的不寻常倾向，其研究可能有助于阐明 IFITM1 在细胞中的抗病毒和促癌功能。