NMR backbone assignment of the Cε4 domain of immunoglobulin E

Abstract

Immunoglobulin E (IgE) plays a central role in allergic reactions. IgE is a dynamic molecule that is capable of undergoing large conformational changes. X-ray crystal structures of the Fc region of IgE in complex with various ligands have shown that IgE-Fc can exist in extended and various bent conformations. IgE-Fc consists of three domains: Cε2, Cε3 and Cε4. While the complete NMR backbone assignments of the Cε2 and Cε3 domains have been reported previously, the Cε4 domain has not been assigned. Here, we report the complete backbone assignment of the Cε4 homodimer. Cε4 can be used as a model system to study dynamics and allostery in IgE, as both molecules exist as homodimers and exhibit similar binding properties to a number of ligands.

Keywords: Backbone assignment; Cε4; Homodimer; Immunoglobulin E; NMR.

Fig. 1

a The ¹⁵N-HSQC of Cε4 where the peaks are labelled with their residue assignment. The assignments for the peaks in the region labelled with a rectangle are shown in b. In both a and b, the assigned peaks are labelled with the residues in the tag labelled in red. (c, left panel) shows the sequence of Cε4 with the unassigned residues in the tag coloured blue, the assigned residues coloured red and the unassigned residues coloured black and (c, right panel) a cartoon representation of the structure of Cε4 (from PDB: 1O0V). One monomer is coloured dark grey and the other is coloured light grey. The ¹⁵N-HSQC of Cε4 was generated using CPPNmr Analysis and the cartoon illustration of Cε4 was generated using PyMOL. The figures were annotated using Adobe Photoshop (Adobe)

Fig. 2

Figure showing the secondary chemical shifts for Cε4, based on the Cα and Cβ chemical shifts of Cε4. The figure also shows the secondary structure of Cε4 based on the IgE-Fc crystal structure (PDB: 1O0V)