Pressure-Volume Properties of Molten Globule

熔球的压力-体积特性

基本信息

批准号：
12680649
负责人：
NITTA Katsutoshi
金额：
$ 2.18万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

We had already obtained the following result concerning to the volumetric behavior of the typical and classical molten globule of bovine α-lactalbumin : although the volume of α-lactalbumin decreased during the conformational change ftom native to molten-globule (ΔV【approximately equal】 - 60 cm^3/mol)s, that from molten-globule to fully-unfolded state was nearly 0 cm^3/mol (Kobashigawa et al., Protein Sci., 8, 2765-2772(1999)). In the case of egg-white lysozyme, which does not show stable molten-globule and unfolds and refolds with two-state mechanism, the unfolding behavior under the pressure up to 100 Mpa cannot be explained with two-state mechanism, especially at lower temperature (0 〜 20℃). It suggests that the volumetric behavior is somewhat complicated. The molten globule of hen egg-white lysozyme is stabilized under pressure. Canine milk lysozyme shows extremely stable molten globule. The thermal behavior of canine milk lysozyme was investigated with differential scanning calorimetry and it is shown that the conformational changes from native to molten-globule and molten-globule to unfolded state are clearly separated to each other. This is because that the molten-globule state of canine milk lysozyme is extremely stable as compared to those of α-lactalbumins and conventional lysozymes. From mutational investigation, this stability is originated from the formation of hydrophobic cluster of His21, Ile56, Ala93 and Val109 in molten-globule state. As the origin of the stability is hydrophobic interaction, the volume is anticipated to increase during the conformational change from molten-globule to unfolded state. However, we have not yet proved it experimentally due to the lack of stability of the instrument under higher temperatures.

We had already obtained the following result concerning to the volumetric behavior of the typical and classical molten globule of bovine α-lactalbumin: although the volume of α-lactalbumin improved during the conformational change ftrom native to molten-globule (ΔV [approximately equal] - 60 cm^3/mol)s, that from molten-globule to fully-unfolded state was almost 0 cm^3/mol （Kobashigawa等人，蛋白质科学，8，2765-2772（1999））。在没有显示稳定的熔融球体并以两态机制的形式展开和反射的卵白溶菌酶的情况下，无法用两态机制来解释压力下的展开行为，尤其是在较低的温度下（0至20°C）。这表明体积行为有些复杂。在压力下稳定了母鸡卵白溶菌酶的熔融球。犬牛奶溶菌酶显示出极为稳定的熔融球。研究了犬牛奶溶菌酶的热行为，并通过不同的扫描量热法进行了研究，这表明构象的变化从天然到熔融全球和熔融全球到展开状态的构象变化显然是相互分离的。这是因为与α-乳脂蛋白和常规溶菌酶相比，犬牛奶溶菌酶的熔融球状状态非常稳定。从突变投资中，这种稳定性是从熔融全球状态下HIS21，ILE56，ALA93和Val109的疏水簇的形成而原来的。由于稳定性的起源是疏水相互作用，因此预计在从熔融全球到展开状态的构象变化期间的体积会增加。但是，由于仪器在较高的温度下缺乏稳定性，我们尚未通过实验证明它。