Protein PTHB1 (BBS9)

The BBSome complex is supposed to function as a coat complex required for sorting of certain membrane proteins to the primary cilia. The BBSome complex is required for ciliogenesis but is dispensable for centriolar satellite function.

This ciliogenic function is mediated in part by the Rab8 GDP/GTP exchange factor, which localizes to the basal body and contacts the BBSome. Rab8(GTP) enters the primary cilium and promotes expansion of the ciliary membrane.