FIG. 6.

Glutaraldehyde cross-linking demonstrates the solely trimeric state of the 230-kDa complexes. Affinity-purified and gel filtration-separated 230-kDa complexes were glutaraldehyde cross-linked for 15 min at room temperature before the reaction was stopped. Samples were completely reduced, separated by 5% SDS-PAGE, and analyzed by Western blotting with the antibody WE 83.4. If the glutaraldehyde concentration was raised above 0.06%, the trimer band slowly faded away, since the WE 83.4 epitope is known to contain a lysine residue (54). Molecular mass markers (in kDa) are noted at the right of blots. RF indicates the running front of the gel.