ISDA

Entry Detail

PDB ID:

5ML9

Keywords:

Title:

Cocrystal structure of Fc gamma receptor IIIa interacting with Affimer F4, a specific binding protein which blocks IgG binding to the receptor.

Biological Source:

Source Organism:

Homo sapiens, synthetic construct

Host Organism:

Homo sapiens

PDB Version:

Deposition Date:

2016-12-06

Release Date:

2017-12-13

Method Details:

Experimental Method:

X-RAY DIFFRACTION

Resolution:

2.35 Å

R-Value Free:

0.27

R-Value Work:

0.21

R-Value Observed:

0.22

Space Group:

P 21 21 21

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Macromolecular Entities

Protein Blast

Polymer Type:polypeptide(L)
Description:Low affinity immunoglobulin gamma Fc region receptor III-A
Chain IDs:A
Chain Length:175
Number of Molecules:1
Biological Source:Homo sapiens

UniProt ID:P08637 Pfam ID:PF13895

Polymer Type:polypeptide(L)
Description:Affimer F4 with specificity for Fc gamma receptor IIIa
Chain IDs:B
Chain Length:115
Number of Molecules:1
Biological Source:synthetic construct

Ligand Molecules

NAG

PEG

SO4

Primary Citation

Affimer proteins inhibit immune complex binding to Fc gamma RIIIa with high specificity through competitive and allosteric modes of action.

Robinson, J.I, Baxter, E.W, Owen, R.L, Thomsen, M, Tomlinson, D.C, Waterhouse, M.P, Win, S.J, Nettleship, J.E, Tiede, C, Foster, R.J, Owens, R.J, Fishwick, C.W.G, Harris, S.A, Goldman, A, McPherson, M.J, Morgan, A.W.Show

Proc. Natl. Acad. Sci. U.S.A. 115 E72 E81 (2018)

PMID: 29247053 DOI: 10.1073/pnas.1707856115

Abstact

Protein-protein interactions are essential for the control of cellular functions and are critical for regulation of the immune system. One example is the binding of Fc regions of IgG to the Fc gamma receptors (FcγRs). High sequence identity (98%) between the genes encoding FcγRIIIa (expressed on macrophages and natural killer cells) and FcγRIIIb (expressed on neutrophils) has prevented the development of monospecific agents against these therapeutic targets. We now report the identification of FcγRIIIa-specific artificial binding proteins called "Affimer" that block IgG binding and abrogate FcγRIIIa-mediated downstream effector functions in macrophages, namely TNF release and phagocytosis. Cocrystal structures and molecular dynamics simulations have revealed the structural basis of this specificity for two Affimer proteins: One binds directly to the Fc binding site, whereas the other acts allosterically.

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Primary Citation of related structures