RAB27A is part of the small GTPase superfamily, Rab family. RAB27A is membrane-bound and participates in protein transport and small GTPase mediated signal transduction. Mutations in this RAB27A are associated with Griscelli syndrome type 2. RAB27A is involved in cytotoxic granule exocytosis in lymphocytes.RAB27A is necessary for both granule maturation and granule docking and priming at the immunologic synapse.