Figure 3 - full size

 

Figure 3.
(a) (4-DAPA)-HA was incubated with HLA-DR1 as described for (4-DAPA)-RSMA[4]L, and the complex formed was purified by gel filtration. Fluorescence of DR-(4-DAPA)-HA was compared with that of the free peptide. (b) Activation of HA1.7 T-cell receptor hybridoma by antigen-presenting cells pulsed with HA (filled circles) or (4-DAPA)-HA (closed triangles) peptides. T-cell activation reported as counts per minute (c.p.m.) measured in a thymidine incorporation bioassay for IL-2 as secreted by activated T cells. Error bars indicate s.d. of triplicate measurements. (c–e) Crystal structure of (4-DAPA)-HA bound to DR1. (c) (4-DAPA)-HA peptide shown with surface representation of the DR1 peptide binding site, with the 4-DAPA side chain shown with yellow bonds extending down into the P1 pocket (top); unmodified HA peptide from the crystal structure of the DR1-HA-SEC (3B2) complex (PDB ID 1JWU) shown after alignment of MHC peptide binding domain, with tyrosine side chain at the P1 position shown with cyan bonds (bottom). (d) 2F[o] - F[c] omit map of the region around the P1 pocket with all residues shown removed from the model before map calculation. (e) Section through the P1 pocket, showing the HA peptide tyrosine side chain and the (4-DAPA)-HA fluorophore, along with the corresponding ordered water molecules, colored as in c. Panels c–e made using PyMOL^30.

The above figure is reprinted by permission from Macmillan Publishers Ltd: Nat Chem Biol (2007, 3, 222-228) copyright 2007.