The effects of hydrostatic pressure on pertussis toxin-catalyzed ribosylation of G proteins from deep-living macrourid fishes
Abstract
To test the effects of hydrostatic pressure on the coupling of receptors to guanyl nucleotide binding reglatory proteins (G proteins) in transmembrane signaling, pertussis toxin (PTX)-catalyzed [32P]ADP-ribosylation was used to probe the guanyl nucleotide-binding proteins G(i) and G(o) in brain membranes from four marine teleosts. These macrourids, Coryphaenoides pectoralis, Coryphaenoides cinereus, Coryphaenoides filifer and Coryphaenoides armatus, span depths from 200 to 5400 m. Pertussis toxin specifically labelled proteins of 39-41 kDa. The PTX-catalyzed [32P]ADP-ribosylation reaction was linear for 7 h. Added guanyl nucleotides (guanosine 5'-diphosphate (GDP) and guanosine 5'-O-(3-thiotriphosphate)(GTP[S])) at concentrations up to 1000 μM did not affect ribosylation at atmospheric pressure. Under basal conditions the G(i)/G(o) protein population appears to be uncoupled from receptors and bound with GDP. Pressures up to 476 atm were tested in the absence and presence of added guanyl nucleotides, 100 μM GDP and 100 μM GTP[S]. [32P]ADP-ribosylation in brain membranes from the deeper-occurring C. cinereus, C. filifer and C. armatus was not inhibited by increased pressure in the presence of 100 μM GDP. Increasing pressure decreased ribosylation in brain membranes of C. pectoralis. In the presence of 100 μM GTP[S], increased pressure inhibited ribosylation in all species. Pressure appears to enhance the efficacy of GTP[S] in dissociating the heterotrimeric holoprotein. Copyright (C) 2000 Elsevier Science Inc.