Members of this family are integral membrane proteins involved in protein trafficking between the late Golgi and endosome. They may also serve as a receptor for ADP-ribosylation factor-related protein 1 (ARFRP1) [1]. Sys1p is a small integral membrane protein with four predicted transmembrane domains that localises to the Trans Golgi network TGN in yeast and human cells [2].

1: Membrane targeting: getting Arl to the Golgi. Graham TR; Curr Biol. 2004;14:483-485. PMID:15203023

2: Arl1p is involved in transport of the GPI-anchored protein Gas1p from the late Golgi to the plasma membrane. Liu YW, Lee SW, Lee FJ; J Cell Sci. 2006;119:3845-3855. PMID:16926193