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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Principal component analysis of the pH-dependent conformational transitions of bovine β-lactoglobulin monitored by heteronuclear NMR
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Principal component analysis of the pH-dependent conformational transitions of bovine β-lactoglobulin monitored by heteronuclear NMR

机译：异核NMR监测牛β-乳球蛋白pH依赖性构象转变的主成分分析

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摘要

To clarify the pH-dependent conformational transitions of proteins, we propose an approach in which structural changes monitored by heteronuclear sequential quantum correlation (HSQC) spectroscopy were analyzed by using a principal component analysis (PCA). We use bovine β-lactoglobulin, a protein widely used in protein folding studies, as a target. First, we measured HSQC spectra at various pH values and subjected them to a PCA. The analysis revealed three apparent transitions with pK_a values of 2.9, 4.9, and 6.8, consistent with previous reports using different methods. Next, Gdn-HCI-induced unfolding was examined by measuring tryptophan fluorescence at various pH values. Between pH 2 and 8, β-lactoglobulin exhibited a number of structural transitions as well as changes in stability represented by the free energy change of unfolding, △Gu. By combining the NMR and fluorescence results, the change in AGu was suggested to result from the decreased pK_a of some acidic residues. Notably, the native state at neutral pH is destabilized by deprotonation of Glu-89, leading to an increase in the relative population of the intermediate. Thus, the PCA of pH-dependent HSQC spectra provides a more comprehensive understanding of the stability and function of proteins.
机译：为了阐明蛋白质的pH依赖性构象转变，我们提出了一种方法，其中使用主成分分析（PCA）分析了通过异核顺序量子相关（HSQC）光谱监测的结构变化。我们将牛β-乳球蛋白（一种广泛用于蛋白质折叠研究的蛋白质）用作靶标。首先，我们在各种pH值下测量了HSQC光谱，并对其进行了PCA分析。分析显示pK_a值分别为2.9、4.9和6.8的三个明显过渡，这与以前使用不同方法的报告一致。接下来，通过在各种pH值下测量色氨酸荧光来检查Gdn-HCl诱导的展开。在pH 2和8之间，β-乳球蛋白表现出许多结构转变以及以展开的自由能变化△Gu表示的稳定性变化。通过结合NMR和荧光结果，AGu的变化被认为是由于某些酸性残基的pK_a降低所致。值得注意的是，中性pH下的天然状态由于Glu-89的去质子作用而不稳定，从而导致中间体的相对种群增加。因此，pH依赖的HSQC光谱的PCA提供了对蛋白质稳定性和功能的更全面的了解。

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