Identification Of The Key Amino Acids Invovled In The Binding Of HMGL To Its Ligand GalNAc

Carbohydrate recognition domain?CRD?is the structure basis of the binding of lecins to carbohydrate ligands,and different CRD of different kinds of lectins determines selective recognition of carbohydrate residues.Human macrophage galactose-type lectin?hMGL?is one of the most important members of C-type lectin receptors?CLRs?.It can specifically bind to a variety of ligand molecules,thus resulting in immune activation and immune tolerance.It's known now that hMGL can specifically recognize terminal GalNAc in the carbohydrate ligands,but for the key amino acids participating in the binding of its CRD to Gal NAc is not clear.In this study,the GalNAc recognition by hMGL,which including 4 truncated-mutation and 17 single point-mutation in the CRD,was detected on the protein and cellular level by Biolayer Interferometry?BLI?and Flow Cytometry?FCM?,respectively.We analyzed preliminarily the structure basis of the binding of hMGL to GalNAc.Our results showed that Gln240,Asp242,Glu253,Asn265 and Asp266 are very instrumental in the binding of hMGL to GalNAc.Amino acids sequence alignment and simulation analysis of space structure showed that these five amino acids are Ca²⁺binding sites in hMGL and what's more,participate in the recognition of GalNAc.Secondly,our results proved that His257,Asp225,Thr227 and Asp228 also play an important role in the binding of hMGL to GalNAc.Amino acids sequence alignment and simulation analysis of space structure showed that these four amino acids probably play a vital role by contributing to maintain the space structure of Ca²⁺binding sites,rather than participating in the binding to GalNAc directly.Study on the critical amino acids participating in the binding of hMGL to GalNAc helps to reveal the structure basis of the binding of hMGL to its ligands.Futhermore,this will provide important previous basic for the analysis of particular recognition mechanism of different lectins to carbohydrate.