TOPOLOGICAL ANALYSIS OF THE HUMAN BETA(2)-ADRENERGIC RECEPTOR EXPRESSED IN ESCHERICHIA-COLI

We have investigated the topology of the human beta(2)-adrenergic receptor expressed in Escherichia coli, using the genetic method described by Beckwith and coworkers. We found that fusions with alkaline phosphatase beyond a certain point on the human beta(2)-adrenergic receptor sequence were assembled into the bacterial membrane with the same topology as the human beta(2)-adrenergic receptor in the mammalian membrane. The pattern that might have been expected on the basis of the topology of the human beta(2)-adrenergic receptor in mammalian membranes was not reflected in the levels of alkaline phosphatase activity of the fusions occurring between the N-terminal region and positions close to the second external domain. Our data suggest that the correct positioning of the N terminus of the receptor depends on the presence of its C-terminal portions.