title: Hemin regulation of hemoglobin binding by Porphyromonas gingivalis.
abstract: Hemoglobin binding to chemostat-grown hemin-excess and hemin-limited cells of Porphyromonas gingivalis W50, and to cells of the avirulent, beige-pigmenting variant W50/BE1, was quantified. Hemin-excess W50 bound more hemoglobin than hemin-limited W50, mirroring the hemin-binding ability of these cells [Microb Ecol Health Dis 7:9-15, 1994]. In contrast to hemin, hemoglobin binding was not enhanced by sodium dithionite. The hemoglobin-binding capacity of hemin-excess W50/BE1 was below that of hemin-limited W50 and only observed under oxidizing conditions. Scatchard analysis revealed similar affinity constants for hemin-excess and hemin-limited W50, and confirmed a lower binding maximum for the latter. Hemin-excess W50/BE1 displayed cooperative binding of hemoglobin. These differences in binding were reflected in the binding of a horse radish peroxidase-conjugated hemoglobin (HHRPO) in a dot-blot assay. However, neither the 32-kDa hemin-binding protein, nor its 19-kDa heat-modified form, from either hemin-limited W50 or hemin-excess W50/BE1, bound this conjugate. These data indicate that hemoglobin binding by P. gingivalis is hemin-regulated and occurs via a mechanism different from hemin binding.
authors.affiliation: Unit of Oral Biology, Department of Clinical Dental Sciences, The University of Liverpool, Liverpool L69 3BX, UK.
authors.forename: J W
authors.initials: JW
authors.lastname: Smalley
authors.forename: A J
authors.initials: AJ
authors.lastname: Birss
authors.forename: A S
authors.initials: AS
authors.lastname: McKee
authors.forename: P D
authors.initials: PD
authors.lastname: Marsh
mesh_terms: D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D006427:Hemin / Q000008:administration & dosage / Q000494:pharmacology*; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D016966:Porphyromonas gingivalis / Q000187:drug effects* / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects
chemical_list: D006454:Hemoglobins; D008565:Membrane Proteins; D006427:Hemin