Peptide sequence of an antibiotic cecropin from the vector mosquito, Aedes albopictus

We have identified a 35-amino acid antibiotic cecropin secreted by an established mosquito cell line. C7-10 cells from the vector mosquito, Aedes albopictus, were incubated with heat-killed Escherichia coli, and materials secreted into the cell culture supernatant were recovered by acid precipitation. Following batch elution from Sep-Pak C18 cartridges and further purification by reverse phase high performance liquid chromatography (RP-HPLC) a predominant peak of antibacterial activity was characterized by mass spectrometry, amino acid composition analysis, and Edman degradation, yielding the sequence GGLKKLGKKLEGVGKRVFKASEKALPVAVGIKALG. Unlike other cecropins, the peptide was not amidated at the C-terminus. Aedes albopictus Cecropin A (AalCecA) is the first cecropin to be described from a mosquito vector of human disease. Consistent with the classification of mosquitoes among the Dipteran suborder Nematocera, AalCecA shares only 36% amino acid identity with cecropins from Drosophila melanogaster and other Cyclorrhaphid flies, whose mature cecropins share 80% to 100% amino acid identity.