Hew C L, Joshi S, Wang N C, Kao M H, Ananthanarayanan V S
Eur J Biochem. 1985 Aug 15;151(1):167-72. doi: 10.1111/j.1432-1033.1985.tb09081.x.
The amino acid sequences of the two major antifreeze polypeptides (AFP) from the shorthorn sculpin have been determined using an automatic protein sequencer and enzymic digestion. These two polypeptides, SS-3 and SS-8, consist of 33 and 45 amino acid residues respectively. The N-terminal methionyl residue is blocked in both the polypeptides. When aligned for maximum structural similarity these two AFP are 80% homologous, and there appears a deletion of 12 amino acid residues at the N-terminal portion of SS-3. Like the winter flounder AFP, both the sculpin AFP also contain the 11-amino-acid repeat sequences. The secondary structure of the sculpin AFP is mainly alpha-helical as deduced from circular dichroic spectral data. The helical content of SS-8 is high (73%), while that of SS-3 is moderate (about 45%). The latter exhibits a relatively weak antifreeze activity. Removal of the blocked N-terminal residue in SS-8 did not alter the helical content significantly but did reduce the antifreeze activity. Helical contents of proteolytically generated fragments of AFP are much lower, and they are devoid of activity. The alpha-helix in the SS-8 component is seen to be amphiphilic in character. The relevance of this feature to the mechanism of the antifreeze action is briefly discussed.
利用自动蛋白质测序仪和酶解技术，已确定了短角杜父鱼两种主要抗冻多肽（AFP）的氨基酸序列。这两种多肽，即SS - 3和SS - 8，分别由33个和45个氨基酸残基组成。两种多肽的N端甲硫氨酰残基均被封闭。当为获得最大结构相似性而进行比对时，这两种抗冻多肽的同源性为80%，并且在SS - 3的N端部分出现了12个氨基酸残基的缺失。与冬鲽抗冻多肽一样，杜父鱼抗冻多肽也含有11个氨基酸的重复序列。根据圆二色光谱数据推断，杜父鱼抗冻多肽的二级结构主要为α螺旋。SS - 8的螺旋含量很高（73%），而SS - 3的螺旋含量适中（约45%）。后者表现出相对较弱的抗冻活性。去除SS - 8中被封闭的N端残基并没有显著改变螺旋含量，但确实降低了抗冻活性。抗冻多肽经蛋白酶水解产生的片段的螺旋含量要低得多，并且它们没有活性。SS - 8组分中的α螺旋具有两亲性。本文简要讨论了这一特征与抗冻作用机制的相关性。
