Structural basis for the selection of glycosylated substrates by SCF(Fbs1) ubiquitin ligase.
The ubiquitin ligase complex SCF(Fbs1), which contributes to the ubiquitination of glycoproteins, is involved in the endoplasmic reticulum-associated degradation pathway. In SCF ubiquitin ligases, a diverse array of F-box proteins confers substrate specificity. Fbs1/Fbx2, a member of the F-box protein family, recognizes high-mannose oligosaccharides. To elucidate the structural basis of SCF(Fbs1) function, we determined the crystal structures of the Skp1-Fbs1 complex and the sugar-binding domain (SBD) of the Fbs1-glycoprotein complex. The mechanistic model indicated by the structures appears to be well conserved among the SCF ubiquitin ligases. The structure of the SBD-glycoprotein complex indicates that the SBD primarily recognizes Man(3)GlcNAc(2), thereby explaining the broad activity of the enzyme against various glycoproteins. Comparison of two crystal structures of the Skp1-Fbs1 complex revealed the relative motion of a linker segment between the F-box and the SBD domains, which might underlie the ability of the complex to recognize different acceptor lysine residues for ubiquitination.
Mizushima
Tsunehiro
T
Department of Biotechnology, Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
Yoshida
Yukiko
Y
Kumanomidou
Taichi
T
Hasegawa
Yuko
Y
Suzuki
Atsuo
A
Yamane
Takashi
T
Tanaka
Keiji
K
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D018360:Crystallography, X-Ray; D004721:Endoplasmic Reticulum / Q000201:enzymology; D004926:Escherichia coli / Q000235:genetics; D006023:Glycoproteins / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D006860:Hydrogen Bonding; D008358:Mannose / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012260:Ribonucleases / Q000737:chemistry / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D055672:Static Electricity; D013379:Substrate Specificity
D006023:Glycoproteins; D009844:Oligosaccharides; D044843:SKP Cullin F-Box Protein Ligases; D012260:Ribonucleases; D008358:Mannose