 |
PDBsum entry 4fl3
|
|
|
|
References listed in PDB file
|
 |
|
Key reference
|
|
|
Title
|
|
Structural and biophysical characterization of the syk activation switch.
|
|
|
Authors
|
|
U.Grädler,
D.Schwarz,
V.Dresing,
D.Musil,
J.Bomke,
M.Frech,
H.Greiner,
S.Jäkel,
T.Rysiok,
D.Müller-Pompalla,
A.Wegener.
|
|
|
Ref.
|
|
J Mol Biol, 2013,
425,
309-333.
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
Syk is an essential non-receptor tyrosine kinase in intracellular immunological
signaling, and the control of Syk kinase function is considered as a valuable
target for pharmacological intervention in autoimmune or inflammation diseases.
Upon immune receptor stimulation, the kinase activity of Syk is regulated by
binding of phosphorylated immune receptor tyrosine-based activating motifs
(pITAMs) to the N-terminal tandem Src homology 2 (tSH2) domain and by
autophosphorylation with consequences for the molecular structure of the Syk
protein. Here, we present the first crystal structures of full-length Syk
(fl-Syk) as wild type and as Y348F,Y352F mutant forms in complex with AMP-PNP
revealing an autoinhibited conformation. The comparison with the crystal
structure of the truncated Syk kinase domain in complex with AMP-PNP taken
together with ligand binding studies by surface plasmon resonance (SPR) suggests
conformational differences in the ATP sites of autoinhibited and activated Syk
forms. This hypothesis was corroborated by studying the thermodynamic and
kinetic interaction of three published Syk inhibitors with isothermal titration
calorimetry and SPR, respectively. We further demonstrate the modulation of
inhibitor binding affinities in the presence of pITAM and discuss the observed
differences of thermodynamic and kinetic signatures. The functional relevance of
pITAM binding to fl-Syk was confirmed by a strong stimulation of in vitro
autophosphorylation. A structural feedback mechanism on the kinase domain upon
pITAM binding to the tSH2 domain is discussed in analogy of the related family
kinase ZAP-70 (Zeta-chain-associated protein kinase 70). Surprisingly, we
observed distinct conformations of the tSH2 domain and the activation switch
including Tyr348 and Tyr352 in the interdomain linker of Syk in comparison to
ZAP-70.
|
|
|
|
|
|
|
