Molecular cloning and characterization of prophenoloxidase in the black tiger shrimp, Penaeus monodon

A cDNA encoding shrimp, Penaeus monodon, prophenoloxidase (proPO) was obtai ned bi screening a hemocyte library by plaque hybridization using a proPO c DNA fragment from freshwater crayfish, Pacifastacus leniusculus. as a probe . The 3.002 bp cDNA contains an open reading frame of 2,121 bp and a 881 bp 3'-unsaturated region. The molecular mass of the deduced amino acid sequen ce (688 amino acids) is 78.700 Da with an estimated pi of 5.8. Two putative copper binding sites are present and they have a highly conserved sequence around these sites. No signal peptide was detected in the shrimp proPO, as has been previously shown to be the case for all arthropod proPOs cloned s o far. The cleavage site of rymogen activation is likely to be between Arg 44 and Val 45. A tentative complement-like motif (GCGWPQHM) is also present . Shrimp proPO mRNA is synthesized in the hemocytes and not in the hepatopa ncreas. Comparison of amino acid sequences showed that shrimp proPO is more closely related to another crustacean proPO, namely crayfish, than to the insect proPOs. (C) 1999 Elsevier Science Ltd. All rights reserved.