Fig. 5.

Models of the complexes formed by UTP (1) with the P2Y₂ (a) and P2Y₄ (b) receptors. The nucleotide binding pockets are highly conserved in the two receptors [23]. The only two sites of divergence can be found in two residues located in TM2 and EL2 (represented with balls and sticks) in proximity to the uracil-binding pocket. To the left of each detailed binding site is a schematic representation of the entire receptor structure complexed with UTP. In the tube representations the receptor is colored according to residue positions, with a spectrum of colors that ranges from red (N-terminus) to purple (C-terminus): TM1 is in orange, TM2 in ochre, TM3 in yellow, TM4 in green, TM4 in cyan, TM5 in blue, TM7 in purple.