Method for obtaining G protein-coupled receptor (GPCR) diffraction-quality crystals employing a monoclonal antibody that binds to the third intracellular loop (IL3)

1. A method for obtaining crystals of a G protein-coupled receptor (GPCR), comprising:

a) contacting said GPCR with a monovalent antibody that

i. specifically binds to a three dimensional epitope of the intracellular region 3 (IC3) loop of said GPCR and

ii. stabilizes the relative conformations of the transmembrane region 5 (TM5) and transmembrane region 6 (TM6) of said GPCR,

under conditions that provide for binding of said antibody to said GPCR produce an antibody/GPCR complex;

b) removing unbound antibody from the product of step a); and

c) maintaining the product of step b) under conditions suitable for crystallizing said antibody/GPCR complex thereby producing a crystalline form of said antibody/GPCR complex.

2. The method of claim 1 , wherein said method comprises combining said antibody/GPCR complex with lipids prior to crystallizing said complex.

3. The method of claim 1 , wherein said antibody/GPCR complex is crystallized using a bicelle crystallization method or a cubic-phase crystallization method.

4. The method of claim 1 , wherein said GPCR comprises the IC3 loop of the β2 adrenoreceptor (β2AR).

5. The method of claim 1 , wherein said GPCR is a chimeric GPCR that contains the IC3 loop of β2AR.

6. The method of claim 1 , wherein said GPCR is a chimeric GPCR that comprises amino acid residues I223 to K270 of β2AR.

7. The method of claim 6 , wherein said antibody comprises a light chain comprising the amino acid sequence of SEQ ID NO:1 and a heavy chain comprising the amino acid sequence of SEQ ID NO:2.

8. The method of claim 1 , wherein the antibody is made by:

reconsitituting a GPCR in artificial phospholipid vesicles to make an antigen;

immunizing an animal with said antigen; and

screening a plurality of hybridoma lines obtained from said animal for a hybridoma that produces said antibody.