Enhanced electron transfer by GTP: cross-membrane electron signaling by G-proteins?
Activation of several receptor types is followed by their binding to a G-protein. Prior to transmission of the agonist signal, the G-protein which had affinity for guanosine 5-diphosphate (GDP) binds guanosine 5-triphosphate (GTP) instead. Because evidence exists that several agonist groups activate their receptors by reduction, we evaluated whether the nucleotide associated with G-proteins could enhance electron flow. Using a model system of ferrous iron and ferric cytochrome c, it was determined that substitution of GTP for GDP led to an enhanced reduction of ferric cytochrome c. These results support the concept that cellular activation by certain receptors may involve reductive activation with the participation of GTP and G-proteins. We speculate that GTP, when bound to G-protein, can facilitate electron transfer perhaps from the receptor or the G-protein to the catalytic subunit of the adenylate cyclase enzyme.
Peterson
D A
DA
Medical Service, V.A. Medical Center, Minneapolis, MN 55417.
Gerrard
J M
JM
D000262:Adenylyl Cyclases / Q000737:chemistry; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004579:Electron Transport / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D005609:Free Radicals; D019204:GTP-Binding Proteins / Q000502:physiology*; D006153:Guanosine Diphosphate / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D010084:Oxidation-Reduction; D015398:Signal Transduction
D005290:Ferric Compounds; D005296:Ferrous Compounds; D005609:Free Radicals; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases