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Publication Abstract from PubMed

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.

Structure of a human IgA1 Fab fragment at 1.55 A resolution: potential effect of the constant domains on antigen-affinity modulation.,Correa A, Trajtenberg F, Obal G, Pritsch O, Dighiero G, Oppezzo P, Buschiazzo A Acta Crystallogr D Biol Crystallogr. 2013 Mar;69(Pt 3):388-97. doi:, 10.1107/S0907444912048664. Epub 2013 Feb 16. PMID:23519414^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.