Thermodynamic analysis of interactions between N-linked sugar chains and F-box protein Fbs1

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, Man alpha 1 -> 6Man beta 1 -> 4GlcNAc(2), Man alpha 1 -> 3Mar beta -> 4GlcNAc(2), and Man alpha 1 -> 3(Man alpha 1 -> 6)Man beta 1 -> 4GlcNAc(2) were synthesized and their affinities for Fbs1 were evaluated in comparison with previously synthesized Man(9)GlcNAc(2) and Man(8)GlcNAc(2). These analyses revealed that Man(3)GlcNAc(2) had the strongest affinity and the chitobiose and alpha 1 -> 6 linked Man residue are necessary for Fbs1 to recognize a sugar.