RAB27B, Member RAS Oncogene Family (RAB27B)

Members of the Rab protein family are prenylated, membrane-bound proteins involved in vesicular fusion and trafficking. The predicted 218-amino acid RAB27B protein is 71% identical to RAB27A. RAB3A and RAB3B, the most closely related human Rab proteins, share only 41 to 44% identity with RAB27A and RAB27B, suggesting that the RAB27 proteins are members of a distinct subfamily.

Northern blot analysis revealed that RAB27B is expressed significantly only in testis, in which the predominant transcript was 1.4 kb in size. An 8-kb mRNA of unknown origin was detected in many tissues. Recombinant RAB27A and RAB27B exhibited GTP-binding activity in vitro.