CLONING AND CHARACTERIZATION OF CDNAS ENCODING THE ANTIBACTERIAL PEPTIDE, DEFENSIN-A, FROM THE MOSQUITO, AEDES-AEGYPTI

Insect defensins are cationic, inducible antibacterial peptides. Four full-length cDNAs encoding defensin A from the mosquito Aedes aegypti were cloned using polymerase chain reaction (PCR) and Sequenced, All f our cDNAs are 473 base pairs long, bearing an open reading frame of 98 amino acids with a few substitutions in the signal peptide domain, Th e deduced amino acid sequence of Aedes aegypti defensin (AaDef) contai ns a signal peptide sequence of 18 amino acids followed by a 40-amino acid putative propeptide domain and a 40-amino acid mature peptide dom ain, The mature peptide, with a predicted M(r) of 4148, shows 80% iden tity and 93% similarity to Phormia defensin A, and is identical to the peptide sequencing data for mosquito defensin A of Lowenberger et al, (1995) and B of Chalk et al, (1995), There are three potential phosph orylation sites but no glycosylation sites detected in AaDef, Three pu tative disulfide linkages between cysteines, characteristic of insect defensins, are conserved in AaDef. Aedes aegypti defensin mRNA is prod uced in response to a bacterial challenge; it is dramatically enhanced 6 h after bacterial injection, continues to increase through 24 h, an d is maintained at high levels until at least 30 h post-bacterial inje ction, Copyright (C) 1996 Published by Elsevier Science Ltd.