Thermodynamic Analysis of Interactions between N-Linked Sugar Chains and F-Box Protein Fbs1

Abstract
Fbs1 is a recently discovered F-box protein that was proposed to recognize high-mannose-type asparagine-linked glycoprotein sugar chains. To reveal the specificity of Fbs1, Manα1→6Manβ1→4GlcNAc2, Manα1→3Manβ1→4GlcNAc2, and Manα1→3(Manα1→ 6)Manβ1→4GlcNAc2 were synthesized and their affinities for Fbs1 were evaluated in comparison with previously synthesized Man9GlcNAc2 and Man8GlcNAc2. These analyses revealed that Man3GlcNAc2 had the strongest affinity and the chitobiose and α1→6 linked Man residue are necessary for Fbs1 to recognize a sugar.