Endocytosis of cell surface proteins is mediated by a complex molecular machinery that assembles on the inner surface of the plasma membrane. This gene encodes one of two human homologs of the Drosophila melanogaster stoned B protein. This protein is related to components of the endocytic machinery and exhibits a modular structure consisting of an N-terminal proline-rich domain, a central region of homology specific to the human stoned B-like proteins, and a C-terminal region homologous to the mu subunits of adaptor protein (AP) complexes. Co-transcription of this gene and the neighboring downstream gene generates a rare transcript (SALF), which encodes a fusion protein comprised of sequence sharing identity with each individual gene product.