F-box proteins that contain sugar-binding domains

F-box proteins are the substrate-recognition subunits of the SCF (Skp1-Cul1-F-box protein) complex, which is the largest known class of E3 ubiquitin ligases. They play important roles in ubiquitin-dependent proteolysis in eukaryotes. The human genome contains about 70 genes for F-box proteins, and at least five homologous F-box proteins containing a conserved motif in their C-termini are thought to recognize sugar chain of N-linked glycoproteins. Among theses, Fbs1 and Fbs2 are perhaps involved in the endoplasmic reticulum-associated degradation pathway. In this review, I focus on the in vivo function of Fbs1 and homologous proteins, novel intracellular oligosaccharide recognition molecules involved in the quality control system.