Fish cathelicidins : novel antimicrobial peptides identified in rainbow trout Oncorhynchus mykiss and Atlantic salmon Salmo salar

• Main Author: Zhang, Jinyi
• Published: University of Aberdeen 2006
• Subjects: 572.6541757
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430907

This thesis reports a novel antimicrobial peptide gene, termed <i>rt</i>CATH_1, found in rainbow trout <i>Oncorhynchus mykiss.  </i>The predicted 216-residue <i>rt</i>CATH_1 prepropeptide consists of three domains: a 22-residue signal peptide, a 128-residue cathelin-like region containing two identifiable cathelicidin family signatures, and a predicted 66-residue C-terminal cationic antimicrobial peptide.  This predicted mature peptide was unique in possessing features of different known (mammalian) cathelicidin subgroups such as the cysteine bridged family and the specific amino-acid rich family.  A 36-residue peptide corresponding to the core part of <i>rt</i>CATH_1 was chemically synthesised and shown to exhibit potent antimicrobial activity.  Thus <i>rt</i>CATH_1 represents the first teleost cathelicidin. Further to the finding of <i>rt</i>CATH_1 gene, three more cathelicidin genes were found in salmonids; two in Atlantic salmon, named <i>as</i>CATH_1 and <i>as</i>CATH_2, and one in rainbow trout named <i>rt</i>CATH_2.  All the four new salmonid cathelicidin genes share the common characteristics of mammalian cathelicidin genes, such as consisting of four exons, and possessing a highly conserved pre-proregion and four invariant cysteines clustered in the C-terminal region of the cathelin-like domain.  Two 36-residue peptides corresponding to the core part of <i>rt</i>CATH_1 and <i>rt</i>CATH_2 were chemically synthesised and shown to exhibit potent antimicrobial activity.  The differential expression between <i>rt</i>CATH_1 and <i>rtCATH_</i>2 were studied.  <i>rt</i>CATH_2 was expressed constitutively in gill, head kidney, intestine, skin and spleen whilst the expression of <i>rt</i>CATH_1 was inducible in gill, head kidney and spleen after bacterial challenge.