title: Insect immunity. Attacins, a family of antibacterial proteins from Hyalophora cecropia.
abstract: Six closely related antibacterial proteins, attacins A-F, were isolated from the hemolymph of immunized pupae of the Cecropia moth, Hyalophora cecropia. Chromatofocusing separated attacins A-F, with isoelectric points between 5.7 and 8.3. Immunological experiments show that the attacins constitute antibacterially active forms of the previously isolated inducible immune protein P5. Their mol. wts., 20-23 K, are similar to that of protein P5, but significantly lower than 28 K found for preP5 synthesized in vitro (see accompanying paper). The six attacins can be divided into two groups according to their amino acid composition and amino-terminal sequences, attacins A-D constitute a basic group and attacins E and F an acidic one. Within each group the forms are very similar. The attacins efficiently killed Escherichia coli and two other Gram-negative bacteria isolated from the gut of a silk worm but they did not act on other Gram-positive and Gram-negative bacteria tested. Only growing cells of E. coli were attacked; cells suspended in phosphate buffer were inert. Besides the cecropins and lysozyme, the attacins represent a third class of antibacterial proteins in the humoral immune system of H. cecropia.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000302:isolation & purification* / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects*; D006458:Hemolymph / Q000032:analysis*; D007301:Insect Hormones / Q000302:isolation & purification* / Q000494:pharmacology; D019476:Insect Proteins; D007915:Lepidoptera / Q000276:immunology*; D009036:Moths / Q000276:immunology*; D011679:Pupa / Q000276:immunology
chemical_list: D000900:Anti-Bacterial Agents; D007301:Insect Hormones; D019476:Insect Proteins; C039711:attacin antibacterial protein, insect