3QNX: Orthorhombic Form Of Human Iga1 Fab Fragment, Sharing Same Fv As Igg

Citation:
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.
PDB ID: 3QNXDownload
MMDB ID: 97222
PDB Deposition Date: 2011/2/9
Updated in MMDB: 2014/03
Experimental Method:
x-ray diffraction
Resolution: 2.2  Å
Source Organism:
Similar Structures:
Biological Unit for 3QNX: dimeric; determined by author and by software (PISA)
Molecular Components in 3QNX
Label Count Molecule
Proteins (2 molecules)
1
FAB Fragment of Immunoglobulin A1 Light Chain
Molecule annotation
1
FAB Fragment of Immunoglobulin A1 Heavy Chain
Molecule annotation
Chemicals (3 molecules)
1
3
* Click molecule labels to explore molecular sequence information.

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