Using semisynthetic fluorescent Rab27A, we demonstrate that although Rab27A can be prenylated by REP-2, this reaction can be effectively inhibited by other Rab proteins, providing a possible explanation for the accumulation of unprenylated Rab27A in choroideremia.
These results raise the possibility that the retinal degeneration in choroideremia results from the deficient geranylgeranylation of Ram/Rab27 or a closely related protein.