Correlation between human lactoferrin binding and colicin susceptibility in Escherichia coli

Abstract

Escherichia coli H10407 demonstrated low '25I-human lactoferrin (IlLf) binding (7%) and was insusceptible to group A (A, El, E2, E3, E6, and K) and group B (B, D, Ta, Ib, and V) colicins. Conversely, a spontaneous HLf high-binding (44%) variant, H10407(Lf), demonstrated an increased susceptibility to both colicin groups.Colicin-insusceptible E. coli wild-type strains 75ColT, 84ColT, and 98lColT showed a low degree of HLf binding, i.e., 4, 8, and 10%, respectively. The HLf binding capacity was high in the corresponding colicin-susceptible mutants 75ColS (43%), 84ColS (32%), and 981ColS (43%). Furthermore, HLf low-(<5%) and high-(>35%) binding E. coli clinical isolates (10 in each category) were tested for susceptibility against 11 colicins. Colicin V susceptibility did not correlate with HLf binding in either categories. However, with the remaining colicins, three distinct HLf-binding, colicin susceptibility patterns were observed; (i) 10 of 10 HLf low-binding strains were colicin insusceptible, (ii) 6 of 10 HLf high-binding strains were also colicin insusceptible, and (iii) the remaining HLf high binders were highly colicin susceptible. Certain proteins in the cell envelope and outer membrane of wild-type H10407 (HLf low binder, colicin insusceptible) showed a lower mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis compared to the corresponding proteins of mutant H10407(Lf) (HLf high binder, colicin susceptible). These mobility differences were also associated with HLf-binding proteins in Western blot (ligand blot) analysis. The wild type showed a smooth form of lipopolysaccharide (LPS) with a distinct ladder of 0-chains, compared to the rough LPS of the mutant.Exogenous smooth LPS from wild-type H10407 inhibited 125T-HLf binding to mutant H10407(Lf) in a dose-dependent manner, while rough LPS was ineffective. These data establish a correlation between HLf binding and colicin susceptibility in E. coli. The LPS seems to be associated with the HLf binding components and the colicin receptors in a similar manner and interferes with the interaction of these eucaryotic and procaryotic antimicrobial agents with E. coli.

Relationship between antibacterial activity and porin binding of lactoferrin in Escherichia coli and Salmonella typhimurium

“…For certain members of the family Enterobacteriaceae, Lf binding to strains with smooth LPS was low or negligible compared with that of their isogenic R mutants with a high Lf-binding capacity (16,48). Our study with the isogenic R mutants of S. typhimurium suggested that the magnitude of Lf binding to whole cells was inversely related to the length of the LPS polysaccharide moiety.…”

“…Our laboratory has previously demonstrated specific binding of Lf in bacteria belonging to the family Enterobactenaceae and has identified porins as the Lf-binding target proteins (15,16,21,35,48). Lf-binding outer membrane proteins are a class of well-conserved molecules that form ion channels and constitute a permeability barrier against various molecules, including antibiotics, in bacteria (36).…”

“…Though porins occur at a high copy number (7), the Lf-binding capacity markedly varied in these bacteria (15,48). The lipopolysaccharide (LPS) type seemed to affect the interaction of Lf with porins in certain wild-type strains (16,48).…”

Effect of chemotype on Escherichia coli interactions with bactericidal proteins

“…Presumably, LPS O-chains shield porins protecting them from interactions with lactoferrin [5]. It was shown that the degree of lactoferrin interaction with cell surface increases with transition from S-to R-structure of LPS in E. coli H10407 [6]. Our findings suggest that core sugars in cells with LPS Ra-structure impede lactoferrin access to porin, in contrast to the short core in cells with LPS Re-structure.…”

Lactoferrin

“…The molecular mechanisms of this bactericidal activity of Lf, which is not related to iron withholding, appears to be quite similar for either Gram-negative or Gram-positive bacteria, resulting in both cases in a perturbation of bacterial membranes. In Gram-negative bacteria, it was observed that Lf specifi cally binds to porins present on the outer membrane [38] and induces the rapid release of lipopolysaccharides (LPSs) which is known to enhance bacterial susceptibility to osmotic shock, to lysozyme and to other antibacterial molecules [39]. In mediating LPS release, Lf appears to act in two ways.…”