Localization of the Mycoplasma pneumoniae cytadherence-accessory proteins HMW1 and HMW4 in the cytoskeletonlike Triton shell

• DOI: 10.1128/jb.173.3.1041-1050.1991
• Publication Date: 2016-11-04T18:18:25Z
• Authors: M K Stevens; D C Krause
• Keywords: Octoxynol; Blotting, Western; Detergents; Membrane Proteins; Antibodies, Bacterial; Immunohistochemistry; Peptide Mapping; Bacterial Adhesion; Mycoplasma pneumoniae; Polyethylene Glycols; 3. Good health; Bacterial Proteins; Antibody Specificity; Microscopy, Electron, Scanning; Microscopy, Immunoelectron; Cytoskeleton

The location of the cytadherence-accessory high-molecular weight proteins 1 and 4 (HMW1/4) within Mycoplasma pneumoniae cells has been studied by both biochemical and electron microscopic techniques. Peptide mapping studies demonstrated that HMW1/4 share almost identical peptide profiles, suggesting that the two proteins are structurally related. Examination of thin sections of M. pneumoniae with antibodies to HMW1/4 and colloidal gold particles revealed distinct labeling of the filamentous extensions of the mycoplasma cells. Labeling was absent on thin sections of a cytadherence-deficient variant lacking HMW1/4. HMW1/4 partitioned in the detergent-insoluble fraction following Triton X-100 extraction, and analysis by sucrose density gradient centrifugation suggested that HMW1/4 are part of a high-molecular-weight, multiprotein complex. These results were confirmed by immunogold labeling of Triton X-100-extracted M. pneumoniae cells incubated with antibodies to HMW1/4: gold particles bound in specific clusters to detergent-insoluble filaments. Finally, immunogold labeling of whole cells revealed that HMW1/4 are exposed on the cell surface, although to a lesser degree than on the cell interior. These findings indicate that HMW1/4 are membrane proteins associated with the cytoskeletonlike triton shell of M. pneumoniae and localized primarily in the filamentous extensions of the mycoplasma cells.