在犬乳溶菌酶的熔球态β折叠区域形成了一个非天然的α螺旋。

A non-native alpha-helix is formed in the beta-sheet region of the molten globule state of canine milk lysozyme.

作者信息

Watanabe Masahiro, Kobashigawa Yoshihiro, Aizawa Tomoyasu, Demura Makoto, Nitta Katsutoshi

机构信息

Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.

出版信息

Protein J. 2004 Jul;23(5):335-42. doi: 10.1023/b:jopc.0000032653.30096.41.

DOI:10.1023/b:jopc.0000032653.30096.41

PMID:15328889

Abstract

The native and the molten globule states (N and MG states, respectively) of canine milk lysozyme (CML) were examined by CD spectroscopy and AGADIR algorithm, a helix-coil transition program. It revealed that the helical content of the MG state was higher than that of the N-state, suggesting that non-native alpha-helix is formed in the MG state of CML. Using AGADIR, it indicated the possibility of alpha-helix formation in the third beta-strand region in the MG state. To investigate this possibility, we designed a mutant, Q58P, in which the helical propensity of the MG state was significantly decreased around the third beta-strand region. It appeared that the absolute ellipticity value at 222 nm of the mutant in the MG state was smaller than that of the wild-type protein. It could be assumed that the non-native alpha-helix is formed around the third beta-strand region of wild-type CML in the MG state.

摘要

通过圆二色光谱（CD光谱）和AGADIR算法（一种螺旋-卷曲转变程序）对犬乳溶菌酶（CML）的天然态和熔球态（分别为N态和MG态）进行了研究。结果表明，MG态的螺旋含量高于N态，这表明在CML的MG态中形成了非天然α-螺旋。使用AGADIR算法表明，在MG态的第三条β-链区域有形成α-螺旋的可能性。为了研究这种可能性，我们设计了一个突变体Q58P，在该突变体中，MG态在第三条β-链区域周围的螺旋倾向显著降低。结果显示，MG态突变体在222nm处的绝对椭圆率值小于野生型蛋白。可以推测，在MG态下，野生型CML的第三条β-链区域周围形成了非天然α-螺旋。