The construct is used to monitor phosphoinositide distribution, with the step PH domain being specific for PI(3,4,5)P3.
An αTub84B promoter drives expression of EGFP fused to Tag:PH(step). This tag binds specifically to phosphatidylinositol 3,4,5-trisphosphate (PIP3) and thus the protein produced can be used to monitor the distribution of PIP3 within a cell.