Related Experiment Video
Updated: Jul 5, 2026

Imaging ATG9A, a Multi-Spanning Membrane Protein
Published on: June 16, 2023
A SMAP gene family encoding ARF GTPase-activating proteins and its implication in membrane trafficking
Kenji Tanabe1, Shunsuke Kon, Nobuyuki Ichijo
1Department of Molecular Immunology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
Abstract:
SMAP1 and SMAP2 proteins constitute a subfamily of the Arf-specific GTPase-activating proteins. Both SMAP proteins bind to clathrin heavy chains and are involved in the trafficking of clathrin-coated vesicles. In cells, SMAP1 regulates Arf6-dependent endocytosis of transferrin receptors from the coated pits of the plasma membrane, whereas SMAP2 regulates Arf1-dependent retrograde transport of TGN38 from the early endosome to the trans-Golgi network. The common and distinct features of SMAP1 and SMAP2 activity provide a valuable opportunity to examine the differential regulation of membrane trafficking by these two proteins. In this chapter, we describe several basic experimental procedures that have been used to study the regulation of membrane trafficking using SMAP proteins, including a GAP assay as well as procedures to study the transport of transferrin receptors and TGN38. In addition, a yeast two-hybrid system is described because of its utility in identifying novel molecules that interact with SMAP.
Related Concept Videos
Rab Cascades
Rab Proteins
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
SNAREs and Membrane Fusion
SNAREs exist in pairs that symmetrically interact and catalyze the fusion of the lipid bilayers in vesicle and target organelle. v-SNARE in the vesicle membrane are single polypeptide chains that bind to a complementary t-SNARE, composed of 2...
Microtubule Associated Proteins (MAPs)
Coat Assembly and GTPases
Coat assembly depends on the local availability of phosphatidylinositol phosphates or PIPs and GTP-binding proteins. Adaptor proteins, which link the coat proteins to the membrane, bind to these PIPs and play a crucial role in controlling...
Small GTPases - Ras and Rho
Three regulatory proteins control their activity:

