BINDING BETWEEN LIPOPOLYSACCHARIDE AND CECROPIN-A

Cecropin A (CA), a bioactive peptide, produced significant lethality t o Pantoea agglomerans (PA) at low concentrations. Significant mortalit y occurred immediately after addition of CA. Separate preincubations o f lipopolysaccharides (LPS) from the following bacteria: PA, Serratia marcescens, Escherichia coli (EC), and Salmonella typhimurium with CA were performed prior to the bioassay. CA was also preincubated with di phosphoryl lipid A (DPL-A) from EC and S, minnesota (SM), trilinolein, palmitic, lauric and myristic acids (fatty acids contained in the lip id A of PA-LPS) and bovine brain gangliosides. Spectral analyses to de termine the interaction between glycosphingolipids (sphingomyelin, bov ine brain gangliosides, and galactocerebrosides) and CA were performed . Results showed that all types of LPS and DPL-A as well as the gangli osides studied blocked CA lethality to PA. The level of inhibition of CA antibacterial properties was dependent on LPS and DPL-A concentrati on. The individual fatty acids and trilinolein did not affect CA letha lity to PA. Spectral studies showed complexation between CA and PA-LPS , both types of DPL-A, and the glycosphingolipids. Biological and chem ical analyses confirm that CA binds to the diphosphoryl lipid A moiety of LPS.