Skp1 Forms Multiple Protein Complexes, Including RAVE, a Regulator of V-ATPase Assembly

SCF ubiquitin ligases are composed of Skp1, Cdc53, Hrt1 and one member of a large family of substrate receptors known as F-box proteins (FBPs). Here we report the identification, using sequential rounds of epitope tagging, affinity purification and mass spectrometry, of 16 Skp1 and Cdc53-associated proteins in budding yeast, including all components of SCF, 9 FBPs, Yjr033 (Rav1) and Ydr202 (Rav2). Rav1, Rav2 and Skp1 form a complex that we have named 'regulator of the (H+)-ATPase of the vacuolar and endosomal membranes' (RAVE), which associates with the V1 domain of the vacuolar membrane (H+)-ATPase (V-ATPase). V-ATPases are conserved throughout eukaryotes, and have been implicated in tumour metastasis and multidrug resistance, and here we show that RAVE promotes glucose-triggered assembly of the V-ATPase holoenzyme. Previous systematic genome-wide two-hybrid screens yielded 17 proteins that interact with Skp1 and Cdc53, only 3 of which overlap with those reported here. Thus, our results provide a distinct view of the interactions that link proteins into a comprehensive cellular network.