Figure 7.

The Sl ^17H mutation affects dimer formation on the cell surface. COS-1 cells were transfected with normal KL-1 constructs and mutant Sl^17H constructs containing various COOH-terminal deletions: Sl ^17H-T257, Sl ^17H-R249, and Sl ^17H-A240. 72 h after transfection, cell surface proteins were biotinylated, and cells were treated with the cross-linkers DSS and BS³ (as indicated) for 1 h at 37°C. Cell lysates were fractionated on streptavidin-sepharose columns, the biotinylated fraction was electrophoretically fractionated by SDS-PAGE (12%,) and KL protein products were identified by Western blotting. Arrowheads, KL dimers. *Monomers. Molecular mass (M_r) markers are indicated in kilodaltons.