FIG. 7.

HR2 peptide binds to a triggered form of TM. ASLV-A was incubated on ice with combinations of soluble receptor (sTva), liposomes, and/or the HR2 peptide R99, triggered at 37°C, and then cross-linked on ice. Samples were examined by SDS-PAGE and Western blotting and probed with horseradish peroxidase-conjugated streptavidin to detect biotinylated R99 (R99-Bio). Locations of molecular mass standards are shown on the left of each blot. (A) R99-Bio is detected in a position consistent with binding to triggered, oligomeric TM and can be competed by unlabeled R99. The band labeled TM₉₀ migrates somewhat slower than triggered TM in the absence of HR2 peptide (see Results). Soluble receptor (sTva) and/or liposomes were added to the reaction mixture as indicated. Unlabeled R99 was included either in an equimolar amount (1×) or as a 10-fold excess (10×) to R99-Bio, as shown. (B) Appearance of R99-Bio in the TM₉₀ position is dependent upon incubation time at 37°C. (C) TM₉₀ is efficiently immunoprecipitated by antiserum directed against the TM subunit.