An antibody directed against residues 100-119 within the alpha-helical domain of Galpha(s) defines a novel contact site for beta-adrenergic receptors.
A polyclonal antiserum that recognizes residues 100-119 within the alpha-helical domain of Galpha(s) (K-20) caused a dissociation of G(s) into its component subunits and activated a cholera toxin-sensitive high affinity GTPase. Consistently, the antibody mimicked the stimulatory effects of the beta-adrenergic agonist, isoproterenol, on adenylyl cyclase, which is mediated by Galpha(s), and its inhibitory action on NADPH-dependent H(2)O(2) generation, a Gbetagamma-mediated response. A peptide corresponding to the target sequence of K-20 not only neutralized the receptor-mimetic effects of the antibody but inhibited the whole spectrum of isoproterenol action as well, including its antagonistic effects on adenylyl cyclase and NADPH-dependent H(2)O(2) generation. By contrast, COOH-terminal anti-Galpha(s) selectively inhibited the stimulatory effect of isoproterenol on cAMP formation without affecting its inhibitory effect on NADPH-dependent H(2)O(2) generation. The data are consistent with the concept that beta-adrenergic receptors interact with multiple sites on Galpha(s) each playing a distinct role, and strongly suggest that antibody K-20 defines a novel contact site for beta-adrenergic receptors that localizes to the alpha-helical domain and is essential for eliciting the complete spectrum of beta-adrenergic responses.
Krieger-Brauer
H I
HI
Klinisches Institut für Herzinfarktforschung an der Medizinischen Universitätsklinik Heidelberg, Bergheimerstrasse 58, D-69115 Heidelberg, Germany.
Medda
P K
PK
Hebling
U
U
Kather
H
H
D001665:Binding Sites; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D011487:Protein Conformation; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*
D011943:Receptors, Adrenergic, beta; D006160:Guanosine Triphosphate; D019205:GTP-Binding Protein alpha Subunits, Gs