PDBsum entry 2fcb

Immune system

PDB id: 2fcb

Contents

Protein chain

173 a.a. *

Waters ×150

* Residue conservation analysis

PDB id:

2fcb

Name:

Immune system

Title:

Human fc gamma receptor iib ectodomain (cd32)

Structure:

Protein (fc gamma riib). Chain: a. Fragment: ectodomain. Synonym: cd32. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Cell: b-lymphocyte. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

Resolution:

1.74Å R-factor: 0.194 R-free: 0.279

Authors:

P.Sondermann,R.Huber,U.Jacob

Key ref:

P.Sondermann et al. (1999). Crystal structure of the soluble form of the human fcgamma-receptor IIb: a new member of the immunoglobulin superfamily at 1.7 A resolution. Embo J, 18, 1095-1103. PubMed id: 10064577 DOI: 10.1093/emboj/18.5.1095

Date:

07-Jan-99 Release date: 01-Mar-00

Protein chain

P31994  (FCG2B_HUMAN) -  Low affinity immunoglobulin gamma Fc region receptor II-b from Homo sapiens

Seq: 310 a.a.

Struc: 173 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1093/emboj/18.5.1095

Embo J 18:1095-1103 (1999)

PubMed id: 10064577

Crystal structure of the soluble form of the human fcgamma-receptor IIb: a new member of the immunoglobulin superfamily at 1.7 A resolution.

P.Sondermann, R.Huber, U.Jacob.

ABSTRACT

Fcgamma-receptors (FcgammaRs) represent the link between the humoral and cellular immune responses. Via the binding to FcgammaR-positive cells, immunocomplexes trigger several functions such as endocytosis, antibody-dependent cell-mediated cytotoxity (ADCC) and the release of mediators, making them a valuable target for the modulation of the immune system. We solved the crystal structure of the soluble human Fcgamma-receptor IIb (sFcgammaRIIb) to 1.7 A resolution. The structure reveals two typical immunoglobulin (Ig)-like domains enclosing an angle of approximately 70 degrees, leading to a heart-shaped overall structure. In contrast to the observed flexible arrangement of the domains in other members of the Ig superfamily, the two domains are anchored by several hydrogen bonds. The structure reveals that the residues relevant for IgG binding, which were already partially characterized by mutagenesis studies, are located within the BC, C'E and FG loops between the beta-strands of the second domain. Moreover, we discuss a model for the sFcgammaRIIb:IgG complex. In this model, two FcgammaR molecules bind one IgG molecule with their second domains, while the first domain points away from the complex and is therefore available for binding other cell surface molecules, by which potential immunosuppressing functions could be mediated.

Selected figure(s)

Figure 1.
Figure 1 Overall structure of human sFc RIIb. Stereo ribbon representation of the sFc RIIb structure. The loops supposed to be important for IgG binding are depicted in red with some of the residues within the binding site and the conserved disulfide bridge in ball and stick representation. The potential N-glycosylation sites are shown as green balls. The termini are labelled and the -strands are numbered consecutively for the N-terminal domain in black and for the C-terminal domain in blue. The figure was created using the programs MOLSCRIPT (Kraulis, 1991) and RENDER (Merritt and Murphy, 1994).

Figure 4.
Figure 4 The putative binding sites of Fc RIIb. Solid-surface representations of Fc RIIb as produced with GRASP (Nicholls et al., 1991), with colour coding according to the relative surface potential from negative (red) to positive (blue). (A) The molecule as in Figure 1 by a rotation of 90° counter clockwise around the vertical. (B) The molecule is rotated 90° clockwise around the same axis. Both views show the putative binding regions on the C-terminal (A) and the N-terminal domain (B). The amino acid residues discussed in the text are labelled.

The above figures are reprinted from an Open Access publication published by Macmillan Publishers Ltd: Embo J (1999, 18, 1095-1103) copyright 1999.

Figures were selected by an automated process.