MP1 (MEK partner-1) bound specifically to MEK1 and ERK1 and facilitated their activation.
When overexpressed in cultured cells, MP1 enhanced activation of ERK1 and activation of a reporter driven by the transcription factor ELK1 (MIM.311040).
Expression of MP1 in cells increased binding of ERK1 to MEK1. MP1 apparently functions as an adaptor to enhance the efficiency of the MAP kinase cascade.