Channel catfish, Ictalurus punctatus (Rafinesque), tetraspanin membrane protein family: identification, characterization and phylogenetic analysis of tetraspanin 3 and tetraspanin 7 (CD231) transcripts.

Tetraspanins, a large cell surface protein superfamily characterized by having four transmembrane domains, play many critical roles in physiological and pathological processes. In this study, we report the identification, characterization and phylogenetic analysis of the channel catfish tetraspanin 3 and tetraspanin 7 (CD231) transcripts. The full-length nucleotide sequences of tetraspanin 3 and tetraspanin 7 cDNA have 1,453 and 1,842 base pairs, respectively. Analysis of the nucleotide sequences reveals that each has one open reading frame (ORF). The ORF of tetraspanin 3 appears to encode 241 amino acids with calculated molecular mass of 26.8 kDa, while the ORF of tetraspanin 7 potentially encodes 251 amino acids with calculated molecular mass of 27.9 kDa. By comparison with the human counterparts, the channel catfish tetraspanin 3 and tetraspanin 7 peptides have four transmembrane domains, three intracellular domains and two (small and large) extracellular domains. In addition, several characteristic features critical for structure and functions in mammalian tetraspanins are also conserved in channel catfish tetraspanin 3 and tetraspanin 7. The transcripts were detected by RT-PCR in restrictive organs. These results with those from our previous studies on other channel catfish tetraspanins provide important information for further investigating the roles of various tetraspanins in channel catfish infection with microorganisms.