title: Guanidine extraction enhances the binding of human fibrinogen to group-B streptococci.
abstract: Treatment of group-B streptococci with guanidine chloride significantly enhanced their capacity to bind 125I-labelled fibrinogen. The increase in binding activity was almost proportional in the range of 0.05 M to 6 M guanidine chloride. Repeated extractions with guanidine chloride further increased the capacity of B streptococci to bind the labelled fibrinogen. On the other hand, urea, even at concentrations up to 8 M, did not alter the fibrinogen binding. The enhancement was most pronounced with B streptococci of serotypes III and III-R. Cultivation of these streptococci in Baker and Kasper medium, which is known to stimulate formation of microcapsules, reduced 125I-fibrinogen binding. Subsequent treatment with guanidine increased their binding activity, presumably by facilitating the accessibility of the binding sites.
mesh_terms: D001665:Binding Sites; D005340:Fibrinogen / Q000378:metabolism*; D019791:Guanidine; D006146:Guanidines; D006801:Humans; D066298:In Vitro Techniques; D013292:Streptococcus agalactiae / Q000145:classification / Q000378:metabolism*; D014357:Trypsin
chemical_list: D006146:Guanidines; D005340:Fibrinogen; D014357:Trypsin; D019791:Guanidine