CRYPTIC DOMAINS OF A 60 KDA HEAT-SHOCK PROTEIN OF HELICOBACTER-PYLORIBOUND TO BOVINE LACTOFERRIN

Bovine lactoferrin binds to a 60 kDa heat shock protein of Helicobacte r pylori. Binding ability was related to human immunoglobulin G becaus e bovine lactoferrin binding proteins were isolated by extraction of c ell surface associated proteins with distilled water, applied on IgG-S epharose and nickel sulphate chelate affinity chromatography. Binding was demonstrated by Western blot after purified protein was digested w ith alpha-chymotrypsin and incubated with peroxidase-labeled bovine la ctoferrin. Binding was inhibited by bovine lactoferrin, lactose, rhamn ose, galactose, and two iron-containing proteins, ferritin and haptogl obin. Helicobacter pylori binds ferritin and haptoglobin via charge or hydrophobic interactions because this binding was not inhibited by sp ecific and various glycoproteins or carbohydrates. Carbohydrate moieti es of bovine lactoferrin molecules seem to be involved in binding beca use glycoproteins with similar carbohydrate structures strongly inhibi ted binding. Scatchard plot analysis of the binding of peroxidase-labe led bovine lactoferrin to H. pylori cells yielded a k(d) 2.88 x 10(-6) M. In addition, binding of H. pylori cells to bovine lactoferrin was enhanced when bacteria treated with pepsin or alpha-chymotrypsin after isolation from iron-restricted and iron-containing media.