Western blots of recombinant wild type and mutant MEK 1 showing phospho-specific immunolabeling. Lanes 1 and 2 are wild type MEK 1; lanes 3 and 4 are mutant MEK 1 (Thr 200 Arg). MAP kinase was co-expressed in the samples run in lanes 2 and 4. MEK1 (phospho Thr292) antibody was used (GTX82657).