Studies on new antifreeze protein from the psychrophilic diatom, Fragilariopsis cylindrus

Antifreeze proteins (AFPs) are found in a wide range of species including fishes, plants, etc. They have very characteristic feature that inhibit the growth and recrystallization of ice that forms in intercellular spaces. Two expressed sequence tags (ESTs) were previously identified from salt stress cDNA library in Fragilariopsis cylindrus to have similarities with snow mold AFP. Using bioinformatics tools, we analysed these two AFP-ESTs. Accordingly, by using specially designed primers, the open reading frames (ORFs) subcloned into bacterial and plant expression vectors. The predicted gene product, AfpA, had a molecular mass of 27 kDa. Expression of afpA in Escherichia coli yielded an intracellular 27-kDa protein modified with His-tag. According to bioinformatics data, a comparison between AFP-A and carrot AFP has been carried out.