Involved in cell-type differentiation and morphogenesis. Dephosphorylates casein; in vitro. May also be involved as modulators or transducers in various transmembrane signaling systems. H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Binds 2 magnesium or manganese ions per subunit. Inhibited by 50 mM NaF (sodium fluoride). G proteins are composed of 3 units; alpha, beta and gamma. The alpha chain contains the guanine nucleotide binding site. Moderately expressed during growth. Increases during development, peaking at around 8 hours of development (mound stage) and then decreases gradually during the later stages. Mainly expressed in the prestalk cell population during the later multicellular stages. Required for prestalk specific gene expression and for prespore cell differentiation. Expressed (at protein level). Morphological arrest at the mound stage and a defect in cell-type differentiation. Instead of going through morphogenesis, after 16 hours of development, the mounds disaggregate to form smaller aggregates that eventually produce abnormal looking finger-like structures. In the N-terminal section; belongs to the G-alpha family. In the C-terminal section; belongs to the PP2C family.