The structure of the gene for cecropin B, an antibacterial immune protein from Hyalophora cecropia.

Pupae of the moth Hyalophora cecropia respond to an injection of live bacteria by the production of a potent antibacterial activity. The broad-spectrum property of this activity is due chiefly to two small proteins, cecropins A and B. Sequences of the proteins showed them to be homologous and to contain 37 and 35 amino acid residues respectively. The subsequent isolation of two cDNA clones for cecropin B showed that this protein is made as a prepro molecule composed of 62 amino acid residues. We have now prepared a genomic bank and studied four genomic clones for cecropin B. The coding regions were found in two neighbouring BglII fragments, one 0.79 kb and another varying in size from 3.1 kb to 4.9 kb for different clones. One transcriptional unit for preprocecropin B was sequenced and found to be 1035 bp long with a single intron, 514 bp in size. A conserved, insect specific cap site, ATCATTC, was identified by S1 mapping and primer extension experiments. Indications were found for the presence of multigene families and multicopy genes.