Schematic of glutamate in association with LBD residues. Conserved mGluR LBD residues involved in glutamate binding are shown (underlined) in comparison with the corresponding residues for flatworm Glutamate-like receptors GSMP128940 and GSMD004608. Numbers represent residue location with respect to the mouse mGluR3 sequence. Disagreement at a given position is highlighted in red. GSMP128940 displays overall divergence with the canonical glutamate binding pocket, while GSMD004608 retains only key residues that interact with the glutamate α-carboxylic and α-amino groups.