Molecular characterization of apolipoprotein A-I from the skin mucosa of Cyprinus carpio

Apolipoprotein A-I is the most abundant protein in Cyprinus carpio plasma that plays an important role in lipid transport and protection of the skin by means of its antimicrobial activity. A ۵۲۷ bp cDNA fragment encoding C terminus part of apoA-I from the skin mucosa of common carp was isolated using RT-PCR. After GenBank database searching, a partial sequence containing a coding sequence (CDS) relating to this gene was found. Overlapping of the cDNA fragment with this CDS allowed us to obtain the full-length sequence including non-coding regions. This sequence has ۱۱۷۰bp including a polyA tail of ۱۸ bp plus ۴۵ and ۳۵۴ bp at the ۳'- and ۵'-untranslatedregions, respectively. The complete sequence contained an open reading frame of ۲۵۶ amino containing ۵ amino acid propeptides with a predicted molecular mass of ۲۹.۹۶۷ kDa and theoretical pI of ۶.۱۳.The signal peptide of common carp apoA-I was predicted to have the most likely cleavage site between amino acid positions ۱۷ and ۱۸. Domain analysis of common carp apoA-I showed the conserved domain of Apolipoprotein A۱/A۴/E between amino acid resides ۶۷ to ۲۵۱. The similarity search indicated that common carp apoA-I matched apoA protein from the group of fish with ۴۵-۷۷% similarity, but showed relatively low levels of similarity to its mammalian counterparts (۲۰-۲۸%).It was shown that the secondary structure of C. carpio apoA-I consisted of a-helical predominantly amphipathic in nature and was characterized by the presence of thirteen conserved repeats.

Keywords:

Apolipoprotein A-I , Common carp , Cyprinus carpio , Epidermal mucus , Full-length sequence