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Specific binding of lactoferrin to Escherichia coli isolated from human intestinal infections
Author(s) -
Naidu S. S.,
Erdei J.,
CzirÓK É.,
Kalfas S.,
GadÓ I.,
ThorÉN A.,
Forsgren A.,
Naidu A. S.
Publication year - 1991
Publication title -
apmis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.909
H-Index - 88
eISSN - 1600-0463
pISSN - 0903-4641
DOI - 10.1111/j.1699-0463.1991.tb01311.x
Subject(s) - lactoferrin , microbiology and biotechnology , escherichia coli , binding site , biology , serotype , biochemistry , gene
The degrees of human lactoferrin (HLf) and bovine lactoferrin (BLf) binding in 169 Escherichia coli strains isolated from human intestinal infections, and in an additional 68 strains isolated from healthy individuals, were examined in a 125 I‐labelled protein binding assay. The binding was expressed as a percentage calculated from the total labelled ligand added to bacteria. The HLf and BLf binding to E. coli was in the range 3.7 to 73.4% and 4.8 to 61.6%, respectively. Enterotoxigenic strains demonstrated a significantly higher HLf binding (median = 19%) than enteropathogenic, enteroinvasive, enterohaemorrhagic strains or normal intestinal E. coli isolates (medians 6 to 9). Enteropathogenic strains belonging to serotypes 044 and 0127 demonstrated significantly higher HLf binding compared to O26, O55, O111, O119 and O126. No significant differences in the degree of HLf or BLf binding were found between aerobactin‐producing and non‐producing strains. The interaction was further characterized in a high Lf‐binding EPEC strain, E34663 (serotype O127). The binding was stable in the pH range 4.0 to 7.5, did not dissociate in the presence of 2M NaCl or 2M urea, and reached saturation within two h. Unlabelled HLf and BLf displaced the 125 I‐HLf binding to E34663 in a dose‐dependent manner. Apo‐ and iron‐saturated forms of Lf demonstrated similar binding to E34663. Among various unlabelled subepithelial matrix proteins and carbohydrates tested (in 10 4 ‐fold excess) only fibronectin and fibrinogen caused a moderate inhibition of 125 I‐HLf binding. According to Scatchard plot analysis, 5,400 HLf‐binding sites/cell, with an affinity constant (K a ) of 1.4 × 10 −7 M., were estimated in strain E34663. These data establish the presence of a specific Lf‐binding mechanism in E. coli .