ADP-ribosylation factor-like protein 5B (ARL5B) is a member of a family of proteins which are structurally similar to ADP-ribosylation factors. ARLs and ARFs belong to the RAS superfamily of regulatory GTPases. ARL5B is most closely related to ARL5, with which it shares 80% sequence identity. Furthermore, Human ARL5B shares 100% identity with mouse ARL8 and 71% identity with the Drosophila homolog.