Figure 1: Site-specific incorporation of pBpa in the Grb2 SH2 domain.

(a) Chemical structure of a pBpa residue. The crystal structure (stereo view) of the complex between the Grb2 SH2 domain and a peptide inhibitor with the sequence Glu–phospho-Tyr–Ile–Asn–Gln (in green), which corresponds to residues 1067–1071 of the EGF receptor20. (b) pTyr, phosphotyrosine. Residue 111 is shown in magenta and residues 104, 119, 121 and 143 in cyan. (c) Illustration of a photo-cross-link between pBpa in position 111 of Grb2 and a bound protein. (d) The crystal structure (stereo view) of the complex between the Grb2 SH2 and the peptide inhibitor, in which residues 103–112 on the βD and βD′ strands20 are shown in orange.