Heterotrimeric guanine nucleotide-binding proteins (G proteins) consist of α, β and γ subunits and mediate the effects of hormones, neurotransmitters, chemokines and sensory stimuli. To date, over 20 known Gα subunits have been classified into four families, Gα(s), Gα(i/o), Gα(q) and Gα(12), based on structural and functional similarities (1,2). Phosphorylation of Tyr356 of Gα(q)/Gα(11) is essential for activation of the G protein, since phenylalanine substitution for Tyr356 changes the interaction of Gα with receptors and abolishes ligand-induced IP3 formation (3).
Gα(z) stands out from other G proteins because it lacks an ADP-ribosylation consensus site for pertussis toxin, giving it a possible role in signal transduction pathways resistant to the toxin, such as phospholipase C (4). Gα(z) is phosphorylated and activated by protein kinase C (PKC) at Ser27 (5,6).
