DRD2 and Parkinson disease: In agreement with these speculative points [16,17,41], the rs1800497 variant in DRD2/ANKK1 changes the glutamic acid to lysine (from an amino acid group with a negatively charged side chain to positively charged residue) that might result in a significant protein structure modification that leads to reduced expression of the receptor and the development of neuropsychiatric disorders among PD patients.