Component of the TSET complex, a heterohexamer composed of tstA, tstB, tstC, tstD, tstE and tstF, which may act in plasma membrane turnover. tstA, tstB, tstC and tstD are likely to be the core complex members with tstE and tstF acting as associated scaffold proteins. Knockout cells grow at least as fast as a control axenic strain and differentiation also appears normal with fruiting bodies forming under appropriate stimuli. Uptake of FITC-dextran, an assay for fluid phase endocytosis, is unimpaired while uptake of FM1-43, a membrane marker, is slower than in the control. Belongs to the adaptor complexes small subunit family.