Purification of protein IA from Neisseria gonorrhoeae using monoclonal antibody affinity chromatography

Localization and biochemical characterization of the ORF6 gene product of the Mycoplasma pneumoniae P1 operon

ORF6 represents one of the two open reading frames flanking the P1 attachment protein gene of Mycoplasma pneumoniae in the order ORF4-P1-ORF6 (J.M. Inamine, T.P. Denny, S. Loechel, U. Schaper, C.H. Huang, K.F. Bott, and P.C. Hu, Gene 64:217-219, 1988; J.M. Inamine, S. Loechel, and P.C. Hu, Gene 73:175-183, 1988; C.J. Su, V.V. Tryon, and J.B. Baseman, Infect. Immun. 55:3023-3029, 1987), indicating an operonlike organization. As described previously, we identified two proteins with molecular masses of 40 and 90 kDa (B. Sperker, P.C. Hu, and R. Herrmann, Mol. Microbiol. 5:299-306, 1991) which might represent two cotranslational cleavage fragments of the ORF6 gene product. To determine the site of the putative cotranslational cleavage, the first 10 amino acids of the N terminus of the isolated 90-kDa protein were sequenced. The data are consistent with the DNA-deduced amino acid sequence between amino acid positions 455 and 465 (RAGNSSETDAL). Thus, the cleavage site was identified at amino acid position 455 (R). In this study, the two proteins were localized and biochemically characterized. Both proteins are part of the insoluble fraction of M. pneumoniae as shown by immunoblots of supernatants and pellets of mechanically disrupted cells subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Surface proteolysis followed by SDS-PAGE and Western blot (immunoblot) analysis, covalent labelling of surface-exposed proteins with [125I]iodide and subsequent immunoprecipitation of both radiolabelled proteins, immunofluorescence studies with formalized and living M. pneumoniae, and immunoadsorption experiments provided strong evidence that the 40- and 90-kDa proteins are membrane-associated proteins expressing surface-exposed regions.

Interaction of non-piliated Neisseria gonorrhoeae strain 7122 and protein IA with an epithelial cell monolayer

Studies with [14C] uracil-labelled bacteria revealed that the interaction of Neisseria gonorrhoeae with epithelial cells occurred in a time-dependent reaction which is slightly pH-dependent and optimal at pH 6.5. Immunofluorescence tests and immunoelectron microscopy of ultrathin sections confirmed the attachment of these bacteria to the epithelial cell membrane. The interaction of purified protein I with epithelial cells was time-dependent and reached equilibrium after four hours as shown by tracer experiments with 125I-labeled protein I. Cleavage experiments with trypsin followed by SDS-PAGE and autoradiography indicated that protein I (labeled with 125I) was associated with the membrane of the epithelial cells and only partly accessible by trypsin after its interaction with these mammalian cells. Immunofluorescence tests as well as immunoelectron microscopy with the monoclonal antibody G7A2C and gold-labeled protein A confirmed a dense association pattern of protein I with the cell monolayer.

Monoclonal antibodies against bacteria

Highlights are presented of most recent work in which monoclonal antibodies have been instrumental in the study of bacteria and their products. Topics summarized pertain to human and veterinary medicines, dentistry, phytopathology, ichthyology, and bacterial ecophysiology, differentiation, evolution and methanogenic biotechnology.