English: T4 lysozyme (T4L) was fused to the N-terminus of the β2 adrenergic receptor (β2AR). Modifications of the β2AR to facilitate crystallogenesis.

A. Schematic diagram of T4L-β2AR-ΔICL3 fusion protein used for crystallography. Cyan circles indicate β2AR residues included in the construct. Black circles with white letters indicate the residues deleted from the wild type β2AR sequence. Pink circles indicates the HA signal peptide. Green circles indicate the FLAG tag. Yellow circles indicate the TEV recognition site. Cyan circles with yellow letters indicate the M96T, M98T mutations. Cyan circles with red letters indicate the cysteines involved in disulfide bonds. Gold dashed lines indicate the disulfide bond linkages. Cyan circle with a white letter indicates the N187E mutation. Blue circles indicate the 2-Ala linker. Red circles indicate T4L residues.

B. Schematic diagram of all of the T4L-β2AR-ΔICL3 constructs that were generated and evaluated for expression of functional receptor protein in insect cells. Red bar and circles represent T4L sequence. Cyan bar and circles represent β2AR. Blue circles represent Ala linkers.

doi:10.1371/journal.pone.0046039.g001