Sequence and specificity of two antibacterial proteins involved in insect immunity

Abstract

Immune responses have been described for many different insect species. However, it is generally acknowledged that immune systems must therefore differ from those of vertebrates. An effective humoral immune response has been found in pupae of the cecropia moth, Hyalophora cecropia. The expression of this multicomponent system requires de novo synthesis of RNA and proteins and its broad antibacterial activity is due to at least three independent mechanisms, the most well known of which is the insect lysozyme. However, this enzyme is bactericidal for only a limited number of Gram-positive bacteria. WE recently purified and characterized P9A and P9B, which are two small, basic proteins with potent antibacterial activity against Escherichia coli and several other Gram-negative bacteria. We believe that P9A and P9B plays an important part in the humoral immune responses described previously and that the P9 proteins represent a new class of antibacterial agents for which we propose the name cecropins. We describe here the primary structures of cecropins A and B. We also show that cecropin A is specific for bacteria in contrast to melittin, the main lytic component in bee venom which lyses both bacteria and eukaryotic cells.

Antimicrobial Peptides, Skin Infections, and Atopic Dermatitis

“…31 The peptide was devoid of disulfide bonds, had a linear alpha-helical structure, and exhibited antimicrobial activity against gram negative bacteria. This family was classified under the cecropin family of AMPs.…”

NK-lysin of channel catfish: Gene triplication, sequence variation, and expression analysis

“…The first class comprises mainly linear, helical, and amphipathic peptides without disulphide bonds. Well-known examples of this class are cecropins (Steiner et al, 1981). The second class includes linear peptides with an over-representation of a single amino acid, such as histatin 5 (Oppenheim et al, 1988).…”

Antibacterial activity of secretolytin, a chromogranin B‐derived peptide (614–626), is correlated with peptide structure

“…peptides with very potent antibacterial activity, that were first isolated from the hemolymph of Drosophila [8], then from the giant silk moth, Hyalophora cecropia [9,10], and subsequently from a wide range of other insects [11]. Later, an antibacterial peptide with 33% homology to insect cecropins was isolated from porcine small intestine [12].…”