Interaction of lactoferrin with Escherichia coli cells and correlation with antibacterial activity.
It has been established that the antimicrobial activity of lactoferrin towards Escherichia coli is enhanced by a direct contact between the protein and the microbial cell and that, in the case of E. coli K-12 strains, an antibacterial activity of lactoferrin unrelated to iron withdrawal is present. Evidence is now reported that lactoferrin binds to surface structures expressed in E. coli K-12 strains grown in either an "excess" or "stress" of iron. Under the experimental conditions used, lactoferrin binding both in the apo and in the iron-saturated form yields a maximum of 1.6 X 10(5) bound molecules/E. coli K-12 cell; the amount of lactoferrin bound does not depend on the expression of the iron-regulated outer membrane proteins. In contrast, lactoferrin does not bind to E. coli clinical isolates. Apo-lactoferrin (at 500 micrograms/ml in a chemically defined medium) inhibits the growth of E. coli K-12 strains but not of clinical isolates. These findings suggest that the antibacterial activity of the protein could be associated to its binding to the cell surface.
Visca
P
P
Istituto di Microbiologia, Facoltà di Medicina e Chirurgia, Roma, Italy.
Dalmastri
C
C
Verzili
D
D
Antonini
G
G
Chiancone
E
E
Valenti
P
P
D000042:Absorption; D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D001667:Binding, Competitive; D003087:Colicins; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D007781:Lactoferrin / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003087:Colicins; C007104:colicin immunity proteins; D007501:Iron; D007781:Lactoferrin