title: In vivo and in vitro interactions of the Bombyx mori chymotrypsin inhibitor b1 with Escherichia coli.
abstract: Various chymotrypsin inhibitors occur in the hemolymph of silkworm larvae. Interaction of chymotrypsin inhibitor b1 (CI-b1) with Escherichia coli was examined from the viewpoint of action against invading bacteria. Injection of dead E. coli cells into larva reduced the CI-b1 content of the hemolymph, suggesting in vivo binding of CI-b1 to the outer membrane of the cell. Results from incubation of E. coli in cell-free hemolymph in the presence or absence of lipopolysaccharide indicated that CI-b1 is the only CI bound to E. coli and that it interacts with lipopolysaccharide. CI-b1 formed a complex with lipopolysaccharide in vitro; the value of the dissociation constant was relatively large. Inhibitory activity of CI-b1 changed insignificantly in mixture with lipopolysaccharide. CI-b1 affected the growth of E. coli but never worked lethally. CI-b1 is speculated to be a mediator that scavenges intruding bacteria rather than a direct anti-bacterial factor. This is the first report confirming that CI-b1 is a lipopolysaccharide binding protein.
authors.affiliation: Laboratories of Insect Genetic Resources, Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
authors.forename: Ningjia
authors.initials: N
authors.lastname: He
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Aso
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujii
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Banno
authors.forename: Kohji
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D012831:Bombyx / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism; D002455:Cell Division; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D004926:Escherichia coli / Q000166:cytology / Q000378:metabolism*; D006458:Hemolymph / Q000378:metabolism; D007814:Larva / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D002918:Chymotrypsin; C117569:chymotrypsin C