IDENTIFICATION OF CERTAIN SEQUENCES IN THE 3RD CYTOPLASMIC LOOP OF D-4 DOPAMINE-RECEPTOR THAT SUPPRESS THE BACTERIAL EXPRESSION

To study the functional roles of dopamine receptors, we decided to rai se antibodies against these proteins. To make antigen, we expressed th e whole 3rd cytoplasmic loop of dopamine receptors in a fusion protein with glutathione-S-transferase (CST). For D-2 and D-3 receptors, it w as successful to express and purify fusion proteins for the whole 3rd cytoplasmic loops. However, we could not express the fusion protein fo r the whole 3rd cytoplasmic loop of D-4 dopamine receptor in the bacte ria. To study the causes that prevent the bacterial expression of the GST-fusion protein of the 3rd cytoplasmic loop of D-4 dopamine recepto r, we conducted more detailed studies on D-4 dopamine receptor. To loc ate the region which prevents bacterial expression, we made sequential constructs in the 3rd cytoplasmic loop decreasing the size step by st ep, and confirmed their expressions in the SDS PACE. It was found that certain regions of 3rd cytoplasmic loop of D-4 dopamine receptor, loc ated in N-terminal side of the 3rd cytoplasmic loop of D-4 dopamine re ceptor suppress the bacterial expression of fusion protein.