|
pubmed:abstractText |
Three apparently distinct pertussis toxin (PTX)-sensitive substrates, with Mrs of 39, 40 and 41 kDa, were identified in membranes prepared from the sino-atrial (SA) node and right atrium of bovine heart. Based on their biochemical characterization, the effects of guanine nucleotides/MgCl2 on their PTX-catalyzed [32P]ADP ribosylation, and the PTX-induced decrease in radiolabelled agonist high-affinity binding to muscarinic acetylcholine receptors present in these membranes, we tentatively identify these proteins as the alpha-subunits of the G0 and Gi subtypes of G-proteins. These results indicate that PTX alters the G-protein modulation of SA nodal and atrial muscarinic acetylcholine receptors by disrupting at least one of a group of PTX-sensitive G-proteins present in these tissues.
|
