Type II 항동결단백질의 진화: 그 기원과 positive selection에 관한 연구

Abstract

The type II AFPs consist of two subtypes, Calcium-dependent and Calcium-independent AFP. It is unclear whether they have a single or multiple origins. In this study, we made an attempt to investigate the phylogenetic relationships of the type II AFPs with sequence data, using MrBayes and PAML. The results show that the type II AFP are monophylogenetic, and that they have evolved through the positive selection mechanism. The positively selected sites are located not only the region homologous with CaBS (Ca2+-binding site)) in C-type lectin(the upper half), but also the lower half of the AFP molecule. These results suggest that the lower half be involved in ice-binding, supporting the hyphothesis based on quantum mechanics (Cheng Y. et. al., 2002), and site directed mutation (Loewen MC. et. al., 1998).