Regulation of protein phosphorylation within the MKK1-ERK2 complex by MP1 and the MP1*P14 heterodimer.
MEK partner 1 (MP1) and P14 are small proteins that modulate the Raf-MKK1/2-ERK1/2 pathway. To examine the biochemical basis for their function a fluorescent form of MP1 was prepared by labeling Cys-74 with fluorescein. Using this protein it was shown that MP1 binds unactivated ERK1, ERK2 and a constitutively active form of MKK1 (MKK1G7B) with dissociation constants of 9.7+/-1.6, 3.3+/-0.6 and 2.2+/-0.5 microM, respectively. MP1 inhibits the ability of activated ERK2 to phosphorylate the transcription factor Ets-1. Both MP1 and the MP1*P14 complex inhibit the ability of activated ERK2 to phosphorylate MKK1G7B, thus impeding feedback inhibition. In contrast, MP1 and the P14*MP1 complex enhance the ability of MKK1G7B to phosphorylate ERK2, when ERK2 is present at a low concentration, but not when it is present at a high concentration. Thus, MP1 and the MP1*P14 complex have the potential to differentially modulate activating and inhibiting signals in the Raf-MKK1/2-ERK1/2 pathway.
Brahma
Amrita
A
Division of Medicinal Chemistry, University of Texas, Austin, TX 78712-0252, USA.
Dalby
Kevin N
KN
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D019281:Dimerization; D005454:Fluorescence Polarization; D007700:Kinetics; D048369:MAP Kinase Kinase 1 / Q000378:metabolism*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D008954:Models, Biological; D010766:Phosphorylation; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction
D048868:Adaptor Proteins, Signal Transducing; C426009:LAMTOR2 protein, mouse; C114559:Lamtor3 protein, mouse; D011506:Proteins; D011993:Recombinant Fusion Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048369:MAP Kinase Kinase 1