Progesterone receptor membrane component 1 (PGRMC1) binds heme via a surface-exposed site and displays some structural resemblance to cytochrome b5 despite their different functions. In the case of PGRMC1, it is the protein interaction with drug-metabolizing cytochrome P450s and the epidermal growth factor receptor that has garnered the most attention. These interactions are thought to result in a compromised ability to metabolize common chemotherapy agents and to enhance cancer cell proliferation. X-ray crystallography and immunoprecipitation data have suggested that heme-mediated PGRMC1 dimers are important for facilitating these interactions. However, more recent studies have called into question the requirement of heme binding for PGRMC1 dimerization. Our study employs spectroscopic and computational methods to probe and define heme binding and its impact on PGRMC1 dimerization. Fluorescence, electron paramagnetic resonance and circular dichroism spectroscopies confirm heme binding to apo-PGRMC1 and were used to demonstrate the stabilizing effect of heme on the wild-type protein. We also utilized variants (C129S and Y113F) to precisely define the contributions of disulfide bonds and direct heme coordination to PGRMC1 dimerization. Understanding the key factors involved in these processes has important implications for downstream protein–protein interactions that may influence the metabolism of chemotherapeutic agents. This work opens avenues for deeper exploration into the physiological significance of the truncated-PGRMC1 model and developing design principles for potential therapeutics to target PGRMC1 dimerization and downstream interactions.

中文翻译：

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定义 PGRMC1 中血红素结合的要求并确定影响蛋白质二聚化的关键元素

黄体酮受体膜成分 1 (PGRMC1) 通过表面暴露位点结合血红素，尽管功能不同，但与细胞色素 b5 表现出一些结构相似性。就 PGRMC1 而言，最受关注的是与药物代谢细胞色素 P450 和表皮生长因子受体的蛋白质相互作用。这些相互作用被认为会导致普通化疗药物的代谢能力和增强癌细胞增殖的能力受损。 X 射线晶体学和免疫沉淀数据表明，血红素介导的 PGRMC1 二聚体对于促进这些相互作用非常重要。然而，最近的研究对 PGRMC1 二聚化是否需要血红素结合提出了质疑。我们的研究采用光谱和计算方法来探测和定义血红素结合及其对 PGRMC1 二聚化的影响。荧光、电子顺磁共振和圆二色光谱证实了血红素与 apo-PGRMC1 的结合，并用于证明血红素对野生型蛋白的稳定作用。我们还利用变体（C129S 和 Y113F）来精确定义二硫键和直接血红素配位对 PGRMC1 二聚化的贡献。了解这些过程中涉及的关键因素对于可能影响化疗药物代谢的下游蛋白质-蛋白质相互作用具有重要意义。这项工作为更深入地探索截短的 PGRMC1 模型的生理意义和开发针对 PGRMC1 二聚化和下游相互作用的潜在疗法的设计原则开辟了道路。