Two novel insect defensins from larvae of the cupreous chafer, Anomala cuprea: purification, amino acid sequences and antibacterial activity.
A humoral immune response in larvae of the coleopteran insect, Anomala cuprea has been examined for exploring the molecular basis of host-pathogen interactions. The antibacterial activity against the Gram-positive strain, Micrococcus luteus was detected at a low level in absence of injection. The activity increased strikingly in the hemolymph of the larvae challenged with Escherichia coli, showing the fluctuating profile through a time course, which consists of the static induction phase, the production phase rising to a maximum level, and the reduction phase extending over a long duration. Two peptides were purified and characterized by reverse-phase HPLC, Edman degradation and mass spectrometry. They were isoforms, composed of similar sequences with two amino acid substitutions in 43 residues, and novel members of the insect defensins, cysteine-rich antibacterial peptides. Anomala defensins A and B showed potent activity against Gram-positive bacteria, with slight differences in activity against a few strains of tested bacteria. Anomala defensin B was active at high concentration of 40 microM against the Gram-negative strain, Xenorhabdus japonicus, a pathogen toward the host, A. cuprea larvae.
Yamauchi
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Insect Management Laboratory, Department of Forest Entomology, Forestry and Forest Products Research Institute, P.O. Box 16, Tsukuba Norin Kenkyu Danchi-nai, 305-8687, Ibaraki, Japan. yamauchi@ffpri.affrc.go.jp
D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D001517:Coleoptera; D023082:Defensins / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000502:physiology; D007814:Larva; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010802:Phylogeny; D020539:Sequence Analysis, Protein
D000900:Anti-Bacterial Agents; D023082:Defensins; C444438:defensin A, Anomala cuprea; C444439:defensin B, Anomala cuprea; C058181:insect defensin A