title: Haemin-binding proteins of Porphyromonas gingivalis W50 grown in a chemostat under haemin-limitation.
abstract: Porphyromonas gingivalis W50 was grown in a chemostat at pH 7.3 under haemin-limitation and haemin-excess at a constant mean doubling time of 6.9 h. Outer membranes (OM) were extracted from whole cells using EDTA and compared by SDS-PAGE. Haemin-limited cells expressed novel outer membrane proteins (OMPs) of mol. mass 115, 113 and 19 kDa when samples were solubilized at 100 degrees C. A 46 kDa OMP was observed in haemin-excess cells but not in those from haemin-limited conditions. Tetramethylbenzidine (TMBZ) staining of gels, after OM solubilization at 20 degrees C, was used to detect haemin-binding proteins (HBPs). HBPs were observed only in OM from haemin-limited cells. The major HBP (mol. mass 32.4 kDa) corresponded to a similar sized Kenacid-blue-stained protein which was not observed in haemin-excess-derived OM. Haemin-limited cells and OM displayed a ladder-like series of Kenacid-blue-stained proteins. Lighter TMBZ-stained proteins of mol. mass 51, 53, 56 and 60 kDa, with mobilities corresponding to those of silver-stained LPS components, were observed in haemin-limited OM. No soluble HBPs were detected extracellularly. The greater number of HBPs expressed by cells grown under haemin-limitation may reflect an additional cell surface receptor system for haemin acquisition under low environmental levels of this essential cofactor.
authors.affiliation: Department of Clinical Dental Sciences, University of Liverpool, 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: D001425:Bacterial Outer Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D001560:Benzidines; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000302:isolation & purification / Q000378:metabolism*; D006427:Hemin / Q000378:metabolism*; D016966:Porphyromonas gingivalis / Q000254:growth & development / Q000378:metabolism*; D013194:Staining and Labeling
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001560:Benzidines; D002352:Carrier Proteins; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; C021758:3,3',5,5'-tetramethylbenzidine; D006427:Hemin