The secondary structure analyses of proteins hold immense importance in the field of protein science because it plays a vital role in its hierarchical classification. It is the most important transitional step in the prediction of the three‐dimensional structure of any protein. The aim of the current study is to quantitatively determine the secondary structure of an important ciliary protein, viz, an MYC‐binding protein‐1 (MYCBP‐1) orthologue, viz, flagellar‐associated protein 174 (FAP174) from the green alga, Chlamydomonas reinhardtii. FAP174 binds to A‐kinase anchoring protein 240 (AKAP240) and has a crucial role to play in ciliary motility. Hence, the biochemical characterization of FAP174 becomes more vital in understanding its molecular function. The accurate secondary structure of FAP174 was investigated through circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) combined with partial least square regression (PLSR) methods. The far‐UV CD spectrum of FAP174 exhibited a positive band at 192 nm and negative bands at 208 and 221 nm, whereas quantification through BeStSel web server revealed 65% α‐helix, approximately 2% of antiparallel β‐sheets, 6% of β‐turns, and 27% of unordered structures. These results were further confirmed by FTIR spectrum of FAP174 that revealed amide I and II bands at 1654 and 1547 cm−1, respectively. And the PLSR calibration models led to the quantification of the secondary structure for FAP174 protein that fairly corroborated with the values obtained by quantifying CD spectrum, these being approximately 54% α‐helix, 0% β‐sheets, approximately 12% β‐turns, and approximately 34% other structures. The recombinant FAP174 protein is therefore considerably α‐helical and has negligible or no β‐sheets.

中文翻译：

---

化学计量学研究结合光谱学量化鞭毛相关蛋白 174 (FAP174) 的二级结构

蛋白质的二级结构分析在蛋白质科学领域具有极其重要的意义，因为它在其层次分类中起着至关重要的作用。它是预测任何蛋白质三维结构中最重要的过渡步骤。本研究的目的是定量确定一种重要的纤毛蛋白的二级结构，即 MYC 结合蛋白 1 (MYCBP-1) 直向同源物，即来自绿藻的鞭毛相关蛋白 174 (FAP174)，莱茵衣藻。FAP174 与 A-激酶锚定蛋白 240 (AKAP240) 结合，在纤毛运动中起关键作用。因此，FAP174 的生化特征对于理解其分子功能变得更加重要。通过圆二色性 (CD) 和傅里叶变换红外光谱 (FTIR) 结合偏最小二乘回归 (PLSR) 方法研究 FAP174 的准确二级结构。FAP174 的远紫外 CD 光谱在 192 nm 处呈现正带，在 208 和 221 nm 处呈现负带，而通过 BeStSel 网络服务器的量化显示 65% 的 α-螺旋，大约 2% 的反平行 β-折叠，6% 的 β - 转和 27% 的无序结构。FAP174 的 FTIR 光谱进一步证实了这些结果，该光谱分别在 1654 和 1547 cm-1 处显示了酰胺 I 和 II 带。PLSR 校准模型导致 FAP174 蛋白二级结构的量化，这与通过量化 CD 光谱获得的值相当证实，这些值约为 54% α-螺旋，0% β-折叠，大约 12% 的 β-转角和大约 34% 的其他结构。因此，重组 FAP174 蛋白具有相当大的 α-螺旋结构，并且几乎没有或没有 β-折叠。