A crustin gene (Amk1) was identified from a haemocyte library of the black tiger shrimp, Penaeus monodon. The full-length cDNA consists of 411 bp encoding a deduced precursor of 136 amino acids with a signal peptide of 17 amino acids. Amk1 contains a hydrophobic and a Gly-rich region at the N-terminus and a 12 conserved cysteine domain (6-DSC) at the C-terminus. Transcripts of Amk1 are mainly detected in haemocytes and gills by RT-PCR analysis. A recombinant Amk1 was overexpressed and purified from Escherichia coli. This has a molecular mass of 43.66 kDa with a predicted pI of 8.23. Antibacterial assays demonstrated that recombinant Amk1 exhibited antibacterial activity against Gram-positive and Gramnegative bacteria with strong inhibition against Staphylococcus aureus and Vibrio harveyi.
