Complete structure, genomic organization, and expression of channel catfish (Ictalurus punctatus, rafinesque 1818) matrix metalloproteinase-9 gene

In this study, the channel catfish (CC) matrix metalloproteinase-9 (MMP-9) gene was cloned, sequenced, and characterized at both the cDNA and the genomic DNA levels. The complete sequence of the CC MMP-9 cDNA consisted of 2,551 nucleotides, including one open reading frame and 5'- and 3'-end untranslated regions. The open reading frame potentially encoded a 686-amino-acid peptide with a calculated molecular mass (without glycosylation) of approximately 77.4 kDa, which included a signal peptide and potentially heavy O-glycosylation sites. CC MMP-9 did not have the tripeptide Arg-Gly-Asp motif. The degree of conservation of the CC MMP-9 amino acid sequence to human and mouse counterparts was 55%, while to those of other fish species was 67-74%. The full-length CC MMP-9 genomic DNA comprised 5,663 nucleotides, much shorter than human or mouse counterparts. The exon-intron structure followed the splice acceptor/ donor consensus rule, and the sequence contained 13 exons. The MMP-9 transcript was constitutively expressed in restrictive CC tissues. This result should provide fundamental information for further exploration of the role of MMP-9 in fish pathophysiology.