Iron protoporphyrin IX-albumin complexing increases the capacity and avidity of its binding to the periodontopathogen Porphyromonas gingivalis

• Published in: Microbial pathogenesis 1999-03, Vol.26 (3), p.131-137
• Main Authors: SMALLEY, J. W, BIRSS, A. J
• Format: Article
• Language: English
• Subjects: Albumins - metabolism; Animals; Bacteriology; Biological and medical sciences; Cattle; Fundamental and applied biological sciences. Psychology; Microbiology; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Periodontitis - microbiology; Porphyromonas gingivalis; Porphyromonas gingivalis - metabolism; Protoporphyrins - metabolism; Serum Albumin, Bovine - metabolism
• ISSN: 0882-4010; 1096-1208
• DOI: 10.1006/mpat.1998.0259

Cells of Porphyromonas gingivalis strains W50 and WPH35 bound albumin and haemalbumin complexes (with 2:1 and 1:1 molar ratios of protein to iron protoporphyrin IX) in a concentration-dependent manner. The binding capacity for both haemalbumins was greater than for albumin. Scatchard analysis of binding to strain W50 revealed monophasic binding for albumin with an association constant (Ka) approximately 10(5)/M. Binding of the haemalbumin complexes was biphasic. The Kas of the lower-affinity binding phases were similar to that for albumin, whilst those for the higher-affinity binding were approximately 20-30-fold greater. It is concluded that both the capacity and avidity for albumin binding to P. gingivalis are increased following haemalbumin complex formation. This phenomenon would enable cells to discriminate between albumin and haem-bearing albumin molecules as a potential source of haem. Such binding behaviour may confer a nutritional and ecological advantage in the periodontal pocket or gingival sulcus under conditions of haem limitation.