PDBsum entry 5bw7

Immune system

PDB id: 5bw7

Contents

Protein chains

212 a.a.

155 a.a.

Ligands

NAG-NAG-BMA-MAN-NAG-GAL-MAN-NAG

NAG-NAG-BMA-MAN-NAG-MAN-NAG

NAG-NAG-BMA-MAN-NAG-MAN-FUC

NAG-NAG-BMA-MAN-NAG

Metals

_CL

Waters ×26

PDB id:

5bw7

Name:

Immune system

Title:

Crystal structure of nonfucosylated fc y296w mutant complexed with bis-glycosylated soluble form of fc gamma receptor iiia

Structure:

Ig gamma-1 chain c region. Chain: a, b. Fragment: unp residues 108-330. Engineered: yes. Mutation: yes. Low affinity immunoglobulin gamma fc region receptor iii-a. Chain: c. Fragment: unp residues 21-193. Synonym: cd16a antigen,fc-gamma riii-alpha,fcriiia,fcr-10,igg fc

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: ighg1. Expressed in: cricetulus griseus. Expression_system_taxid: 10029. Gene: fcgr3a, cd16a, fcg3, fcgr3, igfr3.

Resolution:

3.00Å R-factor: 0.206 R-free: 0.250

Authors:

Y.Isoda,H.Yagi,T.Satoh,M.Shibata-Koyama,K.Masuda,M.Satoh,K.Kato, S.Iida

Key ref:

Y.Isoda et al. (2015). Importance of the Side Chain at Position 296 of Antibody Fc in Interactions with FcγRIIIa and Other Fcγ Receptors. Plos One, 10, e0140120. PubMed id: 26444434 DOI: 10.1371/journal.pone.0140120

Date:

06-Jun-15 Release date: 14-Oct-15

Protein chains

P01857  (IGHG1_HUMAN) -  Immunoglobulin heavy constant gamma 1 from Homo sapiens

Seq: 399 a.a.

Struc: 212 a.a.*

Protein chain

P08637  (FCG3A_HUMAN) -  Low affinity immunoglobulin gamma Fc region receptor III-A from Homo sapiens

Seq: 254 a.a.

Struc: 155 a.a.*

* PDB and UniProt seqs differ at 4 residue positions (black crosses)

DOI no: 10.1371/journal.pone.0140120

Plos One 10:e0140120 (2015)

PubMed id: 26444434

Importance of the Side Chain at Position 296 of Antibody Fc in Interactions with FcγRIIIa and Other Fcγ Receptors.

Y.Isoda, H.Yagi, T.Satoh, M.Shibata-Koyama, K.Masuda, M.Satoh, K.Kato, S.Iida.

ABSTRACT

Antibody-dependent cellular cytotoxicity (ADCC) is an important effector function determining the clinical efficacy of therapeutic antibodies. Core fucose removal from N-glycans on the Fc portion of immunoglobulin G (IgG) improves the binding affinity for Fcγ receptor IIIa (FcγRIIIa) and dramatically enhances ADCC. Our previous structural analyses revealed that Tyr-296 of IgG1-Fc plays a critical role in the interaction with FcγRIIIa, particularly in the enhanced FcγRIIIa binding of nonfucosylated IgG1. However, the importance of the Tyr-296 residue in the antibody in the interaction with various Fcγ receptors has not yet been elucidated. To further clarify the biological importance of this residue, we established comprehensive Tyr-296 mutants as fucosylated and nonfucosylated anti-CD20 IgG1s rituximab variants and examined their binding to recombinant soluble human Fcγ receptors: shFcγRI, shFcγRIIa, shFcγRIIIa, and shFcγRIIIb. Some of the mutations affected the binding of antibody to not only shFcγRIIIa but also shFcγRIIa and shFcγRIIIb, suggesting that the Tyr-296 residue in the antibody was also involved in interactions with FcγRIIa and FcγRIIIb. For FcγRIIIa binding, almost all Tyr-296 variants showed lower binding affinities than the wild-type antibody, irrespective of their core fucosylation, particularly in Y296K and Y296P. Notably, only the Y296W mutant showed improved binding to FcγRIIIa. The 3.00 Å-resolution crystal structure of the nonfucosylated Y296W mutant in complex with shFcγRIIIa harboring two N-glycans revealed that the Tyr-to-Trp substitution increased the number of potential contact atoms in the complex, thus improving the binding of the antibody to shFcγRIIIa. The nonfucosylated Y296W mutant retained high ADCC activity, relative to the nonfucosylated wild-type IgG1, and showed greater binding affinity for FcγRIIa. Our data may improve our understanding of the biological importance of human IgG1-Fc Tyr-296 in interactions with various Fcγ receptors, and have applications in the modulation of the IgG1-Fc function of therapeutic antibodies.