The structure of the MAP2K MEK6 reveals an autoinhibitory dimer.
MAP2Ks are dual-specificity protein kinases functioning at the center of three-tiered MAP kinase modules. The structure of the kinase domain of the MAP2K MEK6 with phosphorylation site mimetic aspartic acid mutations (MEK6/DeltaN/DD) has been solved at 2.3 angstroms resolution. The structure reveals an autoinhibited elongated ellipsoidal dimer. The enzyme adopts an inactive conformation, based upon structural queues, despite the phosphomimetic mutations. Gel filtration and small-angle X-ray scattering analysis confirm that the crystallographically observed ellipsoidal dimer is a feature of MEK6/DeltaN/DD and full-length unphosphorylated wild-type MEK6 in solution. The interface includes the phosphate binding ribbon of each subunit, part of the activation loop, and a rare "arginine stack" between symmetry-related arginine residues in the N-terminal lobe. The autoinhibited structure likely confers specificity on active MAP2Ks. The dimer may also serve the function in unphosphorylated MEK6 of preventing activation loop phosphorylation by inappropriate kinases.
Min
Xiaoshan
X
Department of Biochemistry, The University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-8816, USA.
Akella
Radha
R
He
Haixia
H
Humphreys
John M
JM
Tsutakawa
Susan E
SE
Lee
Seung-Jae
SJ
Tainer
John A
JA
Cobb
Melanie H
MH
Goldsmith
Elizabeth J
EJ
D000595:Amino Acid Sequence; D000818:Animals; D018360:Crystallography, X-Ray; D019281:Dimerization; D004789:Enzyme Activation; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D048669:MAP Kinase Kinase 6 / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011487:Protein Conformation; D051381:Rats; D012542:Scattering, Radiation; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D048369:MAP Kinase Kinase 1; D048669:MAP Kinase Kinase 6