A CALCIUM-43-NMR STUDY OF CALCIUM-BINDING TO AN ACIDIC PROLINE-RICH PHOSPHOPROTEIN FROM HUMAN-SALIVA
A CALCIUM-43-NMR STUDY OF CALCIUM-BINDING TO AN ACIDIC PROLINE-RICH PHOSPHOPROTEIN FROM HUMAN-SALIVA
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DOI：
10.1021/bi00351a011
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发表时间：
1986-02-11
期刊：
影响因子：
2.9
通讯作者：
BENNICK, A
中科院分区：
文献类型：
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作者：
BRAUNLIN, WH;VOGEL, HJ;BENNICK, A
43钙NMR谱线宽度测量的钙结合蛋白A，一种酸性脯氨酸丰富的唾液蛋白，是1个数量级窄于以前观察到的类似分子量的其他蛋白质。相关时间，四极耦合常数，和化学位移估计的钙离子结合到完整的蛋白质（Mr. apprx。10 000）和其30个氨基酸残基长的酸性N-末端TX肽在实验误差内无法区分。这些结果，以及1H NMR弛豫速率测量的结果是指示广泛的运动的蛋白质残基，这反过来又引起了高度的灵活性的蛋白质结合的Ca 2+。对蛋白A、TX肽和去磷酸化TX肽的Ca 2+滴定和pH依赖性测量确立了两个磷酸丝氨酸残基在结合Ca 2+中的重要性。此外，在所有这些蛋白质中相似对称性的43 Ca NMR的比较。没有证据表明蛋白A的高酸性N-末端和弱碱性C-末端区域之间存在相互作用。相比之下，在完整蛋白的pH滴定曲线中观察到的高pH拐点也发现磷酸和脱磷酸TX肽，因此表明N-末端区域中的碱性部分而不是C-末端区域中的碱性部分可能是导致该观察结果的原因。
The 43Ca NMR line width measured for Ca2+ bound to protein A, an acidic proline-rich salivary protein, is 1 order of magnitude narrower than has previously been observed for other proteins of similar molecular weight. The correlation times, quadrupole coupling constants, and chemical shifts estimated for Ca2+ ions bound to the intact protein (Mr .apprx. 10 000) and its 30 amino acids residue long acidic N-terminal TX peptide were indistinguishable within experimental error. These results-as well as the outcome of 1H NMR relaxation rate measurements-are indicative of extensive motions for the protein residues, which in turn give rise to a high degree of flexibility for the protein-bound Ca2+. Ca2+ titration and pH-dependent measurements on protein A, the TX peptide, and the dephosphorylated TX peptide established the importance of the two phosphoserine residues in the binding Ca2+. Moreover, a comparison of the 43Ca NMR of similar symmetry in all these proteins. No evidence was found for a proposed interaction between the highly acidic N-terminal and the weakly basic C-terminal regions of protein A. In contrast, the high pH inflection that was observed in the pH titration curve for the intact protein was also found for the phospho and dephospho TX peptides, thus suggesting that basic moieties in the N-terminal region rather than those in the C-terminal region may be responsible for this observation.