SIGNALING FUNCTIONS AND BIOCHEMICAL-PROPERTIES OF PERTUSSIS TOXIN-RESISTANT G-PROTEINS

Pertussis toxin (PTX) has been widely used as a reagent to characteriz e the involvement of heterotrimeric G-proteins in signalling. This tox in catalyses the ADP-ribosylation of specific G-protein alpha subunits of the G(1) family, and this modification prevents the occurrence of the receptor-G-protein interaction. This review focuses on the biochem ical properties and signalling of those G-proteins historically classi fied as 'PTX-resistant' due to the inability of the toxin to influence signalling through them. These G-proteins include members of the G(q) and G(12) families and one G(i) family member, i.e. G(z). Signalling pathways controlled by these G-proteins are well characterized only fo r G(q) family members, which activate specific isoforms of phospholipa se C, resulting in increases in intracellular calcium and activation o f protein kinase C (PKC), among other responses.