Characterization of mitogen-activated protein kinase (MAPK) dimers.
Phosphorylated ERK2 has an increased capacity to form homodimers relative to unphosphorylated ERK2. We have characterized the nature of the ERK2 dimer and have mutated residues in the crystal dimer interface to examine the impact of dimerization on ERK2 activity. Analysis of the mutants by gel filtration indicates that at least five residues must be mutated simultaneously to produce an ERK2 mutant that is predominantly monomeric. Mutants, whether monomers or dimers, have specific protein kinase activities under fixed assay conditions that are roughly equivalent to wild-type ERK2. The ratio of dimers to monomers is increased as the salt concentration increases, consistent with a strong hydrophobic contribution to the energy of dimer formation. ERK2 dimerization also requires divalent cations. Sedimentation analysis indicates that the related c-Jun N-terminal kinase SAPKalphaI/JNK2 also forms dimers, but dimerization displays no dependence on phosphorylation; the unphosphorylated and phosphorylated forms of the kinase behave similarly, with low micromolar dimer dissociation constants.
Wilsbacher
Julie L
JL
Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, Texas 75390-9041, USA.
Juang
Yu-Chi
YC
Khokhlatchev
Andrei V
AV
Gallagher
Ewen
E
Binns
Derk
D
Goldsmith
Elizabeth J
EJ
Cobb
Melanie H
MH
D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D020928:Mitogen-Activated Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
D020928:Mitogen-Activated Protein Kinases