Structural characterization of a proline-driven conformational switch within the Itk SH2 domain

Abstract

Interleukin-2 tyrosine kinase (Itk) is a T cell-specific kinase required for a proper immune response following T cell receptor engagement. In addition to the kinase domain, Itk is composed of several noncatalytic regulatory domains, including a Src homology 2 (SH2) domain that contains a conformationally heterogeneous Pro residue. Cis-trans isomerization of a single prolyl imide bond within the SH2 domain mediates conformer-specific ligand recognition that may have functional implications in T cell signaling. To better understand the mechanism by which a proline switch regulates ligand binding, we have used NMR spectroscopy to determine two structures of Itk SH2 corresponding to the cis and trans imide bond-containing conformers. The structures indicate that the heterogeneous Pro residue acts as a hinge that modulates ligand recognition by controlling the relative orientation of protein-binding surfaces.

Two-dimensional NMR Study of the Heme Active Site Structure of Chloroperoxidase

“…mational change of Pro 28 . The isomerization of the prolyl imide bond has been recently attributed to the modulation of ligand recognition of proteins by controlling the relative orientation of protein-binding surfaces (86). However, the failure to observe any TOCSY connectivities among these signals makes it impossible to confirm the assignments proposed here.…”

Structural insights into the interaction of the evolutionarily conserved ZPR1 domain tandem with eukaryotic EF1A, receptors, and SMN complexes

“…Although all of the proline residues in the ZPR1 crystal structure adopt the trans configuration, cis isomers might occur in vivo. Indeed, it has been proposed (23) that the highly conserved proline following the invariant aspartic acid might undergo a native state cis-trans isomerization switch analogous to the proline isomerization switch that modulates ligand recognition in the SH2 domain of the IL-2 tyrosine kinase (24). The proline residue in ZPR1 is located at the N terminus of the ␤6/␤7-loop, the conformation of which would necessarily be altered by cis-trans isomerization.…”

Ligand Specificity Modulated by Prolyl Imide Bond Cis/Trans Isomerization in the Itk SH2 Domain: A Quantitative NMR Study

“…We have previously demonstrated that the Asn 286-Pro 287 imide bond in the Itk SH2 domain adopts both the cis and trans conformations in solution. 2,3 Exchange between the conformers is slow on the NMR time scale, leading to the appearance of doubled resonances in NMR spectra for 35 of the 109 SH2 residues (Figure 1b). The structural changes induced by isomerization of the peptidyl prolyl imide bond in the Itk SH2 domain modulate its affinity for both of its ligands.…”