Involved in ubiquitination and subsequent proteasomal degradation of target proteins. Required for both entry into S phase and kinetochore function. Also involved in cyclic AMP (cAMP) pathway, possibly by participating in the assembly or the conformational activation of specific multiprotein complexes. Interacts with SKP1/CBF3D. Part of SCF E3 ubiquitin ligase complexes containing SKP1, CDC53, HRT1 and some F-box proteins. Interacts with CIR1/CDC35. Present with 1340 molecules/cell in log phase SD medium. Belongs to the SGT1 family.