PDBsum entry 4l4j

Immune system

PDB id: 4l4j

Contents

Protein chains

208 a.a.

182 a.a.

Ligands

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

NAG-NAG-BMA-MAN-NAG

GOL

Waters ×409

PDB id:

4l4j

Name:

Immune system

Title:

Crystal structure of fc-fragment of human igg2-sigma antibody

Structure:

Ig gamma-2 chain c region. Chain: a, b. Fragment: ch2, ch3 domains (unp residues 106-326). Engineered: yes. Mutation: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: ighg2. Expressed in: homo sapiens. Expression_system_taxid: 9606. Expression_system_cell: hek 293e

Resolution:

1.92Å R-factor: 0.201 R-free: 0.247

Authors:

A.Teplyakov,T.Malia,G.Gillilang

Key ref:

O.Vafa et al. (2014). An engineered Fc variant of an IgG eliminates all immune effector functions via structural perturbations. Methods, 65, 114-126. PubMed id: 23872058 DOI: 10.1016/j.ymeth.2013.06.035

Date:

07-Jun-13 Release date: 28-Aug-13

Protein chain

P01859  (IGHG2_HUMAN) -  Immunoglobulin heavy constant gamma 2 from Homo sapiens

Seq: 395 a.a.

Struc: 208 a.a.*

Protein chain

P01859  (IGHG2_HUMAN) -  Immunoglobulin heavy constant gamma 2 from Homo sapiens

Seq: 395 a.a.

Struc: 182 a.a.*

* PDB and UniProt seqs differ at 9 residue positions (black crosses)

DOI no: 10.1016/j.ymeth.2013.06.035

Methods 65:114-126 (2014)

PubMed id: 23872058

An engineered Fc variant of an IgG eliminates all immune effector functions via structural perturbations.

O.Vafa, G.L.Gilliland, R.J.Brezski, B.Strake, T.Wilkinson, E.R.Lacy, B.Scallon, A.Teplyakov, T.J.Malia, W.R.Strohl.

ABSTRACT

The Fc variant of IgG2, designated as IgG2σ, was engineered with V234A/G237A /P238S/H268A/V309L/A330S/P331S substitutions to eliminate affinity for Fcγ receptors and C1q complement protein and consequently, immune effector functions. IgG2σ was compared to other previously well-characterized Fc 'muted' variants, including aglycosylated IgG1, IgG2m4 (H268Q/V309L/A330S/P331S, changes to IgG4), and IgG4 ProAlaAla (S228P/L234A/L235A) in its capacity to bind FcγRs and activate various immune-stimulatory responses. In contrast to the previously characterized muted Fc variants, which retain selective FcγR binding and effector functions, IgG2σ shows no detectable binding to the Fcγ receptors in affinity and avidity measurements, nor any detectable antibody-dependent cytotoxicity, phagocytosis, complement activity, or Fc-mediated cytokine release. Moreover, IgG2σ shows minimal immunogenic potential by T-cell epitope analysis. The circulating half-life of IgG2σ in monkeys is extended relative to IgG1 and IgG2, in spite of similar in vitro binding to recombinant FcRn. The three-dimensional structure of the Fc, needed for assessing the basis for the absence of effector function, was compared with that of IgG2 revealing a number of conformational differences near the hinge region of the CH2 domain that result from the amino acid substitutions. Modeling reveals that at least one of the key interactions with FcγRs is disrupted by a conformational change that reorients P329 to a position that prevents it from interacting with conserved W90 and W113 residues of the FcγRs. Inspection of the structure also indicated significant changes to the conformations of D270 and P329 in the CH2 domain that could negatively impact C1q binding. Thus, structural perturbations of the Fc provide a rationale for the loss of function. In toto, these properties of IgG2σ suggest that it is a superior alternative to previously described IgG variants of minimal effector function, for future therapeutic applications of non-immunostimulatory mAb and Fc-fusion platforms.