Molecular cloning and tissue-specific expression of a five-kazal domain serine proteinase inhibitor from crayfish Procambarus clarkii hemocytes

Abstract

A cDNA clone coding for a five-Kazal domain serine proteinase inhibitor was identified from the hemocytes of crayfish Procambarus clarkii by reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The full-length cDNA sequence is 1128 bp long and contains an open reading frame of 834 bp, 74 bp of 5′-untranslated region (UTR), 236 bp of 3′-UTR with a canonical polyadenylation signal sequence AATAAA, and a poly(A) tail. It encodes a polypeptide of 277 amino acids with an estimated molecular mass of 30.27 kDa and a theoretical pI of 8.01. A signal peptide is defined at the N-terminus with a putative cleavage site located after position 16 (VGA-ST). The mature protein consists of 261 amino acids with five Kazal-type domains. The theoretical mass of the mature protein is 28.52 kDa and the theoretical pI is 7.93. The Kazal-type serine proteinase inhibitors (KSPI) is expressed in the hemocytes of crayfish and predicted to inhibit the chymotrypsin and chymotrypsin-like enzymes.