Lipopolysaccharide-binding proteins and their involvement in the bacterial clearance from the hemolymph of the silkworm Bombyx mori

Abstract

Proteins having the ability to bind to Escherichia coli K12W3110 (rough (R) mutant) were isolated and purified by affinity precipitation from the larval hemolymph of the silkworm Bombyx mori. These proteins were found to consist of two components with molecular masses of 43 kDa and 40 kDa by SDS/PAGE. They bound to all E. coli R mutants (Ra, Rb1, Rc, Rd1, and Re) and Salmonella minnesota R mutants. However, they did not bind to smooth types of the above bacteria. They bound to both lipopolysaccharide(LPS)-coated and lipid-A-coated microtiter plates and have similar dissociation constants for LPS and lipid A. This indicates that the binding proteins recognize the lipid A portion of LPS and thus, we have named these proteins BmLBP (B. mori LPS-binding proteins). We also found that BmLBP participated in the clearance of E. coli cells injected into the body cavity of the silkworm.