PDBsum entry 3qny

Immune system

PDB id: 3qny

Contents

Protein chains

218 a.a.

213 a.a.

Ligands

GOL ×2

Waters ×245

PDB id:

3qny

Name:

Immune system

Title:

Monoclinic form of human iga1 fab fragment, sharing same fv as igg

Structure:

Fab fragment of immunoglobulin a1 light chain. Chain: a, c. Fab fragment of immunoglobulin a1 heavy chain. Chain: b, d

Source:

Homo sapiens. Human. Organism_taxid: 9606. Other_details: serum. Other_details: serum

Resolution:

2.30Å R-factor: 0.188 R-free: 0.218

Authors:

F.Trajtenberg,A.Correa,A.Buschiazzo

Key ref:

A.Correa et al. (2013). Structure of a human IgA1 Fab fragment at 1.55 Å resolution: potential effect of the constant domains on antigen-affinity modulation. Acta Crystallogr D Biol Crystallogr, 69, 388-397. PubMed id: 23519414 DOI: 10.1107/S0907444912048664

Date:

09-Feb-11 Release date: 15-Feb-12

Protein chains

No UniProt id for this chain

Struc: 218 a.a.

Protein chains

No UniProt id for this chain

Struc: 213 a.a.

DOI no: 10.1107/S0907444912048664

Acta Crystallogr D Biol Crystallogr 69:388-397 (2013)

PubMed id: 23519414

Structure of a human IgA1 Fab fragment at 1.55 Å resolution: potential effect of the constant domains on antigen-affinity modulation.

A.Correa, F.Trajtenberg, G.Obal, O.Pritsch, G.Dighiero, P.Oppezzo, A.Buschiazzo.

ABSTRACT

Despite being the most abundant class of immunoglobulins in humans and playing central roles in the adaptive immune response, high-resolution structural data are still lacking for the antigen-binding region of human isotype A antibodies (IgAs). The crystal structures of a human Fab fragment of IgA1 in three different crystal forms are now reported. The three-dimensional organization is similar to those of other Fab classes, but FabA1 seems to be more rigid, being constrained by a hydrophobic core in the interface between the variable and constant domains of the heavy chain (VH-CH1) as well as by a disulfide bridge that connects the light and heavy chains, influencing the relative heavy/light-chain orientation. The crystal structure of the same antibody but with a G-isotype CH1 which is reported to display different antigen affinity has also been solved. The differential structural features reveal plausible mechanisms for constant/variable-domain long-distance effects whereby antibody class switching could alter antigen affinity.