TY - JOUR
T1 - The role of oligosaccharide residues of IgG1-Fc in FcgIIb binding
AU - Mimura, Yusuke
AU - Sondermann, P
AU - Ghirlando, R
AU - Lund, John
AU - Young, Stephen
AU - Goodall, Delia
AU - Jefferis, Royston
PY - 2001/11/30
Y1 - 2001/11/30
N2 - Engagement of Fc gamma receptors (Fc gamma Rs) with the Fe region of IgG elicits immune responses by leukocytes. The recent crystal structure of Fc gamma RIII in complex with IgG-Fc has provided details of molecular interactions between these components (Sondermann, P., Huber, R., Oosthuizen, V., and Jacob, U. (2000) Nature 406, 267-273). One of the most intriguing issues is that glycosylation of IgG-Fc is essential for the recognition by Fc gamma Rs although the carbohydrate moieties are on the periphery of the Fc gamma RIII-Fc interface. To better understand the role of Fe glycosylation in Fc gammaR binding we prepared homogeneous glycoforms of IgG-Fc (Cri) and investigated the interactions with a soluble form of Fc gamma RIIb (sFc gamma RIIb). A 1:1 complex stoichiometry was observed in solution at 30 degreesC (K-d, 0.94 muM; DeltaG, - 8.4 kcal mol(-1); DeltaH, -6.5 kcal mol(-1); T DeltaS, 1.9 kcal mol(-1); DeltaC(p), -160 cal mol(-1) K-1). Removal of terminal galactose residues did not alter the thermodynamic parameters significantly. Outer-arm GlcNAc residues contributed significantly to thermal stability of the C(H)2 domains but only slightly to sFc gamma RIIb binding. Truncation of 1,3- and 1,6-arm mannose residues generates a linear trisaccharide core structure and resulted in a significantly decreased affinity, a less exothermic DeltaH, and a more negative DeltaC(p) for sFc gamma RIIb binding, which may result from a conformational change coupled to complex formation. Deglycosylation of the C(H)2 domains abrogated sFc gamma RIIb binding and resulted in the lowest thermal stability accompanied with noncooperative unfolding. These results suggest that truncation of the oligosaccharides of IgG-Fc causes disorder and a closed disposition of the two C(H)2 domains, impairing sFc gamma RIIb binding.
AB - Engagement of Fc gamma receptors (Fc gamma Rs) with the Fe region of IgG elicits immune responses by leukocytes. The recent crystal structure of Fc gamma RIII in complex with IgG-Fc has provided details of molecular interactions between these components (Sondermann, P., Huber, R., Oosthuizen, V., and Jacob, U. (2000) Nature 406, 267-273). One of the most intriguing issues is that glycosylation of IgG-Fc is essential for the recognition by Fc gamma Rs although the carbohydrate moieties are on the periphery of the Fc gamma RIII-Fc interface. To better understand the role of Fe glycosylation in Fc gammaR binding we prepared homogeneous glycoforms of IgG-Fc (Cri) and investigated the interactions with a soluble form of Fc gamma RIIb (sFc gamma RIIb). A 1:1 complex stoichiometry was observed in solution at 30 degreesC (K-d, 0.94 muM; DeltaG, - 8.4 kcal mol(-1); DeltaH, -6.5 kcal mol(-1); T DeltaS, 1.9 kcal mol(-1); DeltaC(p), -160 cal mol(-1) K-1). Removal of terminal galactose residues did not alter the thermodynamic parameters significantly. Outer-arm GlcNAc residues contributed significantly to thermal stability of the C(H)2 domains but only slightly to sFc gamma RIIb binding. Truncation of 1,3- and 1,6-arm mannose residues generates a linear trisaccharide core structure and resulted in a significantly decreased affinity, a less exothermic DeltaH, and a more negative DeltaC(p) for sFc gamma RIIb binding, which may result from a conformational change coupled to complex formation. Deglycosylation of the C(H)2 domains abrogated sFc gamma RIIb binding and resulted in the lowest thermal stability accompanied with noncooperative unfolding. These results suggest that truncation of the oligosaccharides of IgG-Fc causes disorder and a closed disposition of the two C(H)2 domains, impairing sFc gamma RIIb binding.
UR - http://www.scopus.com/inward/record.url?scp=0035824579&partnerID=8YFLogxK
U2 - 10.1074/jbc.M107478200
DO - 10.1074/jbc.M107478200
M3 - Article
C2 - 11567028
SN - 0021-9258
VL - 276
SP - 45539
EP - 45547
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
ER -