Probable substrate-recognition component of a SCF-like ECS (Elongin-Cullin-SOCS-box protein) E3 ubiquitin ligase complex which mediates the ubiquitination and subsequent proteasomal degradation of target proteins. Protein modification; protein ubiquitination. Component of the probable SCF-like ECS(RAB40C) E3 ubiquitin-protein ligase complex which contains CUL5, RNF7/RBX2, Elongin BC complex and RAB40C. Interacts with CUL5, RNF7, ELOB and ELOC. The SOCS box domain mediates the interaction with the Elongin BC complex, an adapter module in different E3 ubiquitin ligase complexes. Belongs to the small GTPase superfamily. Rab family.