bi9b00932_si_001.pdf (5.7 MB)
A Dynamic Switch in Inactive p38γ Leads to an Excited State on the Pathway to an Active Kinase
journal contribution
posted on 2019-12-13, 20:41 authored by Phillip
C. Aoto, Robyn L. Stanfield, Ian A. Wilson, H. Jane Dyson, Peter E. WrightThe inactive state of mitogen-activated protein kinases
(MAPKs)
adopts an open conformation while the active state exists in a compact
form stabilized by phosphorylation. In the active state, eukaryotic
kinases undergo breathing motions related to substrate binding and
product release that have not previously been detected in the inactive
state. However, docking interactions of partner proteins with inactive
MAPK kinases exhibit allostery in binding of activating kinases. Interactions
at a site distant from the activation loop are coupled to the configuration
of the activation loop, suggesting that the inactive state may also
undergo concerted dynamics. X-ray crystallographic studies of nonphosphorylated,
inactive p38γ reveal differences in domain orientations and
active site structure in the two molecules in the asymmetric unit.
One molecule resembles an inactive kinase with an open active site.
The second molecule has a rotation of the N-lobe that leads to partial
compaction of the active site, resulting in a conformation that is
intermediate between the inactive open state and the fully closed
state of the activated kinase. Although the compact state of apo p38γ
displays several of the features of the activated enzyme, it remains
catalytically inert. In solution, the kinase fluctuates on a millisecond
time scale between the open ground state and a weakly populated excited
state that is similar in structure to the compact state observed in
the crystal. The nuclear magnetic resonance and crystal structure
data imply that interconversion between the open and compact states
involves a molecular switch associated with the DFG loop.