Fig. 2. LSP1 associates with the ERK scaffold KSR. Immunoprecipitates of W10 cell lysates were prepared using anti-KSR (lane 3) or anti-MEK1 antibodies (lane 5). No antibodies were added to the control assay (lane 1). Precipitated proteins were first analyzed by western blotting for the presence of LSP1 (A) and subsequently for the presence of KSR (C). The bands visible in lanes 2 and 4 of A represent spill-over from the anti-KSR immunoprecipitate. The position of LSP1 in the anti-KSR and anti-MEK1 precipitates was identified using an anti-LSP1 immunoprecipitate (B). The position of KSR was identified using a whole cell extract of W10 cells (D). KSR, LSP1 and precipitating IgG are indicated at the right. Molecular mass markers (in kDa) are indicated at the left.