Disulfide-linked protein associated with Mycoplasma pneumoniae cytadherence phase variation

Wild-type Mycoplasma pneumoniae possessed a protein with a very high molecular weight under nonreducing conditions (greater than 340,000; designated HMW5); this protein was absent from a noncytadhering phase variant lacking HMW1, 2, 3, and 4. When examined by two-dimensional nonreducing-reducing gel electrophoresis, HMW5 dissociated to yield a single polypeptide spot of molecular weight 190,000 that comigrated with cytadherence phase-variable protein HMW2. Extraction of wild-type mycoplasmas with Triton X-100 revealed the exclusive partitioning of HMW5 with the detergent-insoluble cytoskeletonlike triton shell.