Plasminogen binding and activation by Mycoplasma fermentans

• Published in: Infection and immunity 2001-04, Vol.69 (4), p.1977-1982
• Main Authors: YAVLOVICH, Amichai, HIGAZI, Abd. A.-R, ROTTEM, Shlomo
• Format: Article
• Language: English
• Subjects: Bacterial diseases; Bacteriology; Biological and medical sciences; Cellular Microbiology: Pathogen-Host Cell Molecular Interactions; Experimental bacterial diseases and models; Fundamental and applied biological sciences. Psychology; HeLa Cells; Humans; Infectious diseases; Iodine Radioisotopes; Medical sciences; Microbiology; Mycoplasma fermentans; Mycoplasma fermentans - physiology; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; plasminogen; Plasminogen - metabolism; Tissue Plasminogen Activator - pharmacology; Urokinase-Type Plasminogen Activator - pharmacology
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.69.4.1977-1982.2001

The binding of plasminogen to Mycoplasma fermentans was studied by an immunoblot analysis and by a binding assay using iodine-labeled plasminogen. The binding of 125I-labeled plasminogen was inhibited by unlabeled plasminogen, lysine, and lysine analog epsilon-aminocaproic acid. Partial inhibition was obtained by a plasminogen fragment containing kringles 1 to 3 whereas almost no inhibition was observed with a fragment containing kringle 4. Scatchard analysis revealed a dual-phase interaction, one with a dissociation constant (kd) of 0.5 microM and the second with a kd of 7.5 microM. The estimated numbers of plasminogen molecules bound were calculated to be 110 and 790 per cell, respectively. Autoradiograms of ligand blots containing M. fermentans membrane proteins incubated with 125I-labeled plasminogen identified two plasminogen-binding proteins of about 32 and 55 kDa. The binding of plasminogen to M. fermentans enhances the activation of plasminogen to plasmin by the urokinase-type plasminogen activator (uPA), as monitored by measuring the breakdown of chromogenic substrate S-2251. Enhancement was more pronounced with the low-molecular-weight and the single-chain uPA variants, known to have low plasminogen activator activities. The binding of plasminogen also promotes the invasion of HeLa cells by M. fermentans. Invasion was more pronounced in the presence of uPA, suggesting that the ability of the organism to invade host cells stems not only from its potential to bind plasminogen but also from the activation of plasminogen to plasmin.