Two highly similar, PtdIns(4,5)P2-selective, Gβγ-activated PI3Ks were purified from pig neutrophil cytosol. Both were heterodimers, were composed of a 101 kDa protein and either a 120 kDa or a 117 kDa catalytic subunit, and were activated greater than 100-fold by Gβγs. Peptide sequence-based oligonucleotide probes were used to clone cDNAs for the p120 and p101 species. The cDNA of p120 is highly related to p110γ, while the cDNA of p101 is not substantially related to anything in current databases. The proteins were expressed in and purified from insect and mammalian cells. They bound tightly to one another, both in vivo and in vitro, and in so doing, p101 amplified the effect of Gβγs on the PI3K activity of p120 from less than 2- fold to greater than 100-fold.
Stephens, L. R., Eguinoa, A., Erdjument-Bromage, H., Lui, M., Cooke, F., Coadwell, J., … Hawkins, P. T. (1997). The Gβγ/sensitivity of a PI3K is dependent upon a tightly associated adaptor, p101. Cell, 89(1), 105–114. https://doi.org/10.1016/S0092-8674(00)80187-7