RCSB PDB - 3AYD: Crystal structure of galectin-3 CRD domian complexed with TFN (original) (raw)
Structural basis for distinct binding properties of the human galectins to thomsen-friedenreich antigen
[Bian, C.F.](/search?q=citation.rcsb%5Fauthors:Bian, C.F.), [Zhang, Y.](/search?q=citation.rcsb%5Fauthors:Zhang, Y.), [Sun, H.](/search?q=citation.rcsb%5Fauthors:Sun, H.), [Li, D.F.](/search?q=citation.rcsb%5Fauthors:Li, D.F.), [Wang, D.C.](/search?q=citation.rcsb%5Fauthors:Wang, D.C.)
(2011) PLoS One 6: e25007-e25007
PubMed Abstract:
The Thomsen-Friedenreich (TF or T) antigen, Galβ1-3GalNAcα1-O-Ser/Thr, is the core 1 structure of O-linked mucin type glycans appearing in tumor-associated glycosylation. The TF antigen occurs in about 90% of human cancer cells and is a potential ligand for the human endogenous galectins. It has been reported that human galectin-1 (Gal-1) and galectin-3 (Gal-3) can perform their cancer-related functions via specifically recognizing TF antigen. However, the detailed binding properties have not been clarified and structurally characterized. In this work, first we identified the distinct TF-binding abilities of Gal-1 and Gal-3. The affinity to TF antigen for Gal-3 is two orders of magnitude higher than that for Gal-1. The structures of Gal-3 carbohydrate recognition domain (CRD) complexed with TF antigen and derivatives, TFN and GM1, were then determined. These structures show a unique Glu-water-Arg-water motif-based mode as previously observed in the mushroom galectin AAL. The observation demonstrates that this recognition mode is commonly adopted by TF-binding galectins, either as endogenous or exogenous ones. The detailed structural comparisons between Gal-1 and Gal-3 CRD and mutagenesis experiments reveal that a pentad residue motif ((51)AHGDA(55)) at the loop (g1-L4) connecting β-strands 4 and 5 of Gal-1 produces a serious steric hindrance for TF binding. This motif is the main structural basis for Gal-1 with the low affinity to TF antigen. These findings provide the intrinsic structural elements for regulating the TF-binding activity of Gal-1 in some special conditions and also show certain target and approach for mediating some tumor-related bioactivities of human galectins.
Organizational Affiliation:
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, People's Republic of China.