Abstract
Cecropins A, B, and D are antibacterial peptides of 35-37 amino acids that are synthesized in pupae of the Cecropia moth (Hyalophora cecropia) as a response to a bacterial infection. cDNA cloning has shown that the cecropins are made as preproproteins that are processed in four steps to the mature peptides. We have now cloned the genes for preprocecropins A and D, data that together with earlier work on the B gene has made it possible to deduce the arrangement of the cecropin locus. The genes for the three cecropins are organized in a large cluster spanning 20 kilobases of DNA and for each gene there is one copy/haploid genome. The size of the cluster is in part due to long distances between the genes and to the presence of insertion elements in the introns of the A and D genes. The cecropin genes are not expressed in parallel. Transcripts for cecropins A and B appear within 2 h after injection of live bacteria, they reach a maximum after 48 h, and they are continuously expressed at this level for several days. The D gene has a delayed pattern of expression where transcripts appear within 48-96 h and reach a maximum after 144 h. In consonance is also the production of the mature cecropins A, B, and D where the active cecropins A and B are detected in the hemolymph within 10-24 h while the D form is not detected until 48 h post infection. Control injections with sterile saline produced only a weak induction of the cecropin genes.
Highlights
Cecropins A, B, and D are antibacterial peptides of later confirmed by two-dimensional NMR (Holak et al, 1988)
Cecropia moth (Hyalophora cecropiaa)s a response to lepidoptera like the Chinese oak silk moth Antheraea pernyi a bacterial infection. cDNA cloning has shown that th(eQu et al, 1982), the tobacco hornworm, Manduca sexta cecropins are made as preproproteins that are proc- (Dickinson et al, 1988), and the common silkworm, Bombyx essed in four steps to the mature peptides
The cecropin genesare not expressed in paralleTl.ran- et al, 1990)are synthesized as preproproteins, 62-64 residues scripts for cecropinsA and B appear within 2 h after in size
Summary
CLONING AND EXPRESSION OF A GENECLUSTER ENCODING THREE ANTIBACTERIAL PEPTIDESIN HYALOPHORA CECROPIA*. CDNA sequencing has shown that the cecropins in two moths, Cecropia and Manduca (von Hofsten et al, 1985; distances between the genes and to the presence of Lidholm et al, 1987; Dickinson et al, 1988), and two flies, insertion elements in the introonfsthe A and D genes. The most potent of these components are the threemain cecropins A, B, and D which contain 35-37 amino acid residues with strongly basic NHZterminals and hydrophobic COOH-terminals(Boman and Hultmark, 1987).The cecropins can form two a-helices joined (Kaniaand Natori, 1989) and in Drosophila where three closely linked cecropin genes were sequenced (Kylsten et al, 1990).We nowreport the sequences for the genes for cecropins A and D from Cecropia, data which together with earlier work on the B gene (Xanthopoulos et al, 1988) has permitted a deduction of the cecropin locus in Cecropia.
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