THE BINDING AND UTILIZATION OF HEMOGLOBIN BY PREVOTELLA-INTERMEDIA

Protella intermedia, a putative periodontopathic microorganism, requir es iron for growth. Hemoglobin can be a major source of iron for bacte rial growth in vivo since it is present in the crevicular fluid collec ted from periodontitis sites. Experiments studying the growth of P. in termedia in iron-depleted Todd-Hewitt broth supplemented with human he moglobin showed that the bacteria were able to utilize human hemoglobi n as a source of iron. The uptake of iron from hemoglobin by P. interm edia appears to be initiated by the binding of hemoglobin to the bacte ria as shown by direct binding studies using I-125-labeled human hemog lobin. Scatchard analysis of saturation binding data revealed that I-1 25-labeled human hemoglobin had a dissociation constant (K-d) of 2.53 x 10(-8) M for the receptor on P. intermedia. Binding of labeled hemog lobin to P. intermedia was competitively inhibited by unlabeled human hemoglobin showing that the binding was specific. The ability of bovin e hemoglobin, but not hemin or non-hemoglobin heme-containing compound s, to inhibit binding competitively suggested that the globin moiety o f the hemoglobin molecule is recognized by the hemoglobin binding rece ptors. (C) 1998 Federation of European Microbiological Societies. Publ ished by Elsevier Science B.V.