LAMININ BINDING TO PREVOTELLA-INTERMEDIA

The interaction of laminin (Lm), a basement membrane protein abundant in the periodontium, with 66 strains of Prevotella intermedia isolated from diseased pockets, was tested in a I-125-labeled protein binding assay. The mean binding value was 28% of the total protein added. The binding significantly increased to 35% when the environmental pH decreased from 7 to 6. The Lm interaction was characterized in a highly binding (about 65%) strain, OMGS105. The binding was rapid and required about 1 min and 12 h for 50% and 100% equilibrium respectively. The I-125-Lm binding was maximum in the pH interval 3.0 to 6.5 and could not be displaced by unlabeled Lm or inhibited by other proteins and carbohydrates. The interaction was stable in the presence of NaCl or urea (concentrations up to 4 M) but was dissociated by greater-than-or-equal-to 1 M KSCN. The Lm-binding component was thermolabile and sensitive to proteolytic enzymes. Sodium dodecylsulfate-polyacrylamide gel electrophoresis and Western blot analysis revealed a almost-equal-to 62 kDa Lm-binding protein, both in the whole cell extract and the outer membrane preparation. Weaker binding was also observed to other proteins. These data establish the ability of P intermedia to interact with Lm via certain cell surface proteins, a property that might contribute to the colonization of this bacterium in the periodontal pocket.