The mammalian beta 2-adrenergic receptor: purification and characterization

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Beta 2-adrenergic receptors play crucial roles in regulating various physiological processes.
• Understanding the precise structure and properties of these receptors is essential for drug development and physiological studies.
• Previous studies identified lower molecular weight peptides, potentially due to proteolysis.

Purpose of the Study:

• To solubilize and purify beta 2-adrenergic receptors from hamster, guinea pig, and rat lungs.
• To characterize the molecular properties of the purified receptors.
• To investigate potential evolutionary homology among mammalian beta 2-adrenergic receptors.

Main Methods:

• Receptor solubilization using digitonin.
• Purification via Sepharose-alprenolol affinity chromatography and HPLC.
• Analysis using SDS-PAGE, autoradiography, silver staining, and lectin binding.

Main Results:

• A single peptide of apparent Mr 64,000 was identified in all three species.
• This peptide corresponded to the one labeled by a specific photoaffinity probe.
• Purified receptors exhibited expected beta 2-adrenergic specificity and stereoselectivity in ligand binding.

Conclusions:

• The consistent 64,000 Mr peptide suggests a conserved structure for beta 2-adrenergic receptors across these species.
• Lower molecular weight peptides previously observed may represent proteolyzed forms.
• Significant similarities in peptide mapping and lectin binding indicate evolutionary homology.