ACTH receptor [SEP] found in taxon
receptors. Both human and bovine ACTH receptors are synthesized as 297 residue long proteins with 81% sequence homology. There are currently no available protein X-ray crystallography structures for the ACTH receptor available in the Protein Data Bank; while the ACTH receptor and the β adrenergic receptor are relatively distantly-related with a sequence identity of approximately 26%, MC2R investigators such as David Fridmanis have assumed that the folded surfaces of both receptors that are responsible for binding G should be very similar and use conserved motifs.
The full length
hormone receptors resided on the plasma membrane of cells, direct studies of the activity of ACTH derivatives that had so long eluded researchers finally became a reality. Hofmann and his colleagues isolated plasma membranes from beef adrenals and were able to conduct structure-activity studies with synthetic analogs of ACTH. Importantly they found that substituting Phenylalanine for theTryptophan residue in position 9 produced a peptide that bound to the ACTH receptor without activating it, i.e. and ACTH antagonist.
Return to Biotin Receptor Isolation 
Hofmann came full circle to his early work on