Molecular characterization and gene expression analysis of a metalloprotease from Pacific abalone Haliotis discus hannai

Abstract

We isolated a metalloprotease (MP) homologue from an abalone muscle cDNA library. A 3284-kb full-length cDNA encoding a predicted polypeptide of 667 amino acids was sequenced. The abalone MP Haliotis discus hannai (HdMP) exhibited a domain structure typical of the peptidase M4 family, a 21-amino acid N-terminal hydrophobic signal sequence followed by a long propeptide sequence of 347 amino acids and the mature protease domain comprising 299 amino acids. The mature region contains features characteristic of a zinc protease, including a zinc-binding motif (HEXXH) and an active site. The protein showed 32–38% amino acid sequence identity with other known MP sequences and with a hypothetical protein from owl limpet. The mRNA transcript is expressed in almost all tissues, with high expression in the mantle and adductor muscle of healthy abalones, and is expressed constitutively during the early developmental stages after fertilization. Lipopolysaccharide or poly I:C stimulation induced the expression of the HdMP transcript in the digestive track and gills of abalones. Collectively, these results suggest that HdMP could play multiple roles in defense, the immune response, growth, and regulation of reproduction.