Figure 4.

Removal of intermonomeric disulfide bridges did not cause dissociation of gp64 subunits. Op1D cells were treated with 10 or 30 mM DTT (lanes 1 and 2), or no DTT (lane 3), followed by cross-linking with 5 mM BS³ for 20 min. Reducing SDS-PAGE in absence of cross-linking gave only a monomeric band (lane 4). Cells were lysed in reducing, 1.5% SDS lysis buffer, and analyzed on 4–12% gradient SDS-PAGE gels. The two trimers which formerly migrated as two distinct bands now migrated as a single band. A monomeric band detected in lanes 1, 2, and 3 suggests that cross-linking was not 100% efficient.