Full Sequence and Characterization of Two Insect Defensins: Immune Peptides from the Mosquito Aedes aegypti

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 261; no. 1361; pp. 217 - 221
• Main Authors: Chalk, Rod, Albuquerque, Cleide M. R., Ham, Peter J., Townson, Harold
• Format: Journal Article
• Language: English
• Published: London The Royal Society 22.08.1995
• Subjects: Aedes - genetics; Aedes - immunology; Amino Acid Sequence; Animals; Anti-Infective Agents - chemistry; Anti-Infective Agents - immunology; Antibacterials; Defensins; Diptera - genetics; Diptera - immunology; Electrophoresis; Female; Gels; Hemolymph; Insect biochemistry; Insect biology; Insect Hormones - chemistry; Insect Hormones - genetics; Insect Hormones - immunology; Insect vectors; Molecular Sequence Data; Molecular Weight; Molecules; Mosquitos; Peptides - chemistry; Peptides - genetics; Peptides - immunology; Protein isoforms; Sequence Homology, Amino Acid; Species Specificity
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rspb.1995.0139

We report the complete amino acid sequence and biological activity of two immune peptides, from the yellow fever mosquito Aedes aegypti, that are induced in response to infection. Both peptides display biological activity against the Gram positive microbe Micrococcus luteus and substantial sequence homology to insect defensins, small heat-stable, antibiotic peptides previously described from several non-vector insects. These mosquito peptides, designated Ae. aegypti defensins A and B, are isoforms. Defensin B is the most abundant antibacterial peptide in this species whereas defensin A is much less abundant and carries two amino acid substitutions compared to defensin B, making it more basic in character. Apparent convergence between isoforms from Ae. aegypti and the fleshfly Phormia terranovae is discussed. The synergistic activity previously described between Ae. aegypti immune haemolymph and lysozyme is not caused by these peptides because synergy occurred only at concentrations far outside the physiological range seen in Ae. aegypti.