We report the isolation of a novel antimicrobial peptide, bass hepcidin, from 
the gill of hybrid striped bass, white bass (Morone chrysops) x striped bass (M. 
saxatilis). After the intraperitoneal injection of Micrococcus luteus and 
Escherichia coli, the peptide was purified from HPLC fractions with 
antimicrobial activity against Escherichia coli. Sequencing by Edman degradation 
revealed a 21-residue peptide (GCRFCCNCCPNMSGCGVCCRF) with eight putative 
cysteines. Molecular mass measurements of the native peptide and the reduced and 
alkylated peptide confirmed the sequence with four intramolecular disulfide 
bridges. Peptide sequence homology to human hepcidin and other predicted 
hepcidins, indicated that the peptide is a new member of the hepcidin family. 
Nucleotide sequences for cDNA and genomic DNA were determined for white bass. A 
predicted prepropeptide (85 amino acids) consists of three domains: a signal 
peptide (24 amino acids), prodomain (40 amino acids) and a mature peptide (21 
amino acids). The gene has two introns and three exons. A TATA box and several 
consensus-binding motifs for transcription factors including C/EBP, nuclear 
factor-kappaB, and hepatocyte nuclear factor were found in the region upstream 
of the transcriptional start site. In white bass liver, hepcidin gene expression 
was induced 4500-fold following challenge with the fish pathogen, Streptococcus 
iniae, while expression levels remained low in all other tissues tested. A novel 
antimicrobial peptide from the gill, bass hepcidin, is predominantly expressed 
in the liver and highly inducible by bacterial exposure.