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首页> 美国卫生研究院文献>Clinical Molecular Pathology >Calcium binding and concomitant changes in the structure and heat stability of calprotectin (L1 protein)
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Calcium binding and concomitant changes in the structure and heat stability of calprotectin (L1 protein)

机译：钙结合以及钙卫蛋白（L1蛋白）的结构和热稳定性的随之变化

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Aim—To obtain further data on the structure and conformation of calprotectin, a prominent leucocyte protein found in many species.Methods—The binding of Ca2+ to calprotectin was studied by means of equilibrium dialysis using 45Ca as tracer. The thermal stability and denaturation kinetics of calprotectin were studied by means of differential scanning calorimetry. Con-comitant alterations in optical activity resulting from different conditions were measured. A computer program calculated the parameters to fit different models of protein structure. Ultraviolet spectroscopy gave absorbtion spectra. Sedimentation velocity studies and molecular weight determinations by the low speed (sedimentation) equilibrium technique were performed.Results—A maximum of six calcium ions were bound per calprotectin molecule at 0·7 mM calcium chloride. The apparent dissociation constants were calculated. Ca2+ ions increased the denaturation temperature by 26°K. The enthalpy of denaturation was also increased by Ca2+. Addition of Ca2+ to the buffers caused a gradual change in the near UV circular dichroism spectrum, while only minor changes were seen at wavelengths of 210-240 nm. A gradual increase in the sedimentation coefficient was observed on addition of calcium chloride. The extinction coefficient at 279nm was determined: E279= 2·53·104 M−1 cm−1.Conclusions—Calprotectin can bind six calcium ions. Upon binding, the protein shows distinct conformational changes and increased thermal stability. The former may be of importance for its function, while the biological significance of the latter is unknown.
机译：目的—为了获得有关钙卫蛋白钙的结构和构象的进一步数据，钙卫蛋白是在许多物种中发现的一种突出的白细胞蛋白。方法—利用通过平衡透析研究Ca 2 + 与钙卫蛋白的结合> 45 Ca作为示踪剂。通过差示扫描量热法研究了钙卫蛋白的热稳定性和变性动力学。测量了由不同条件引起的伴随的光学活性变化。计算机程序计算出参数以适合蛋白质结构的不同模型。紫外光谱法得到吸收光谱。通过低速（沉降）平衡技术进行了沉降速度研究和分子量测定。结果-在0·7 mM氯化钙下，每个钙卫蛋白分子最多结合六个钙离子。计算表观解离常数。 Ca 2 + 离子将变性温度提高了26°K。 Ca 2 + 也增加了变性的焓。向缓冲液中添加Ca 2 + 导致近紫外圆二色性光谱逐渐变化，而在210-240 nm波长处仅观察到很小的变化。加入氯化钙后，沉降系数逐渐增加。测定279nm处的消光系数：E279 = 2·53·10 4 M -1 cm -1 。结论—钙卫蛋白可以结合六种钙离子。结合后，蛋白质显示出明显的构象变化和增加的热稳定性。前者对其功能可能很重要，而后者的生物学意义尚不清楚。

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