The protein architecture of the endocytic coat analyzed by FRET

Endocytosis is a fundamental cellular trafficking pathway, which requires an organized assembly of the multiprotein endocytic coat to pull the plasma membrane into the cell. Although the protein composition of the endocytic coat is known, its functional architecture is not well understood. Here we determine the nanoscale organization of the endocytic coat by FRET microscopy in yeast. We assessed proximities of 18 conserved coat-associated proteins and used clathrin subunits and protein truncations as molecular rulers to obtain a high-resolution protein map of the coat. Furthermore, we followed rearrangements of coat proteins during membrane invagination and their binding dynamics at the endocytic site. We show that the endocytic coat is stratified into several functional layers situated above and below the clathrin lattice with key proteins transversing through the lattice deeply into the cytoplasm. We propose that this conserved design enables an efficient and regulated function of the endocytic coat during endocytosis.