Glycosylation is influential in murine IgG3 self-association.
In mice and humans, antibodies of the IgG3 isotype are unique in that they spontaneously self-associate. A consequence is the formation of cryoglobulins from some, but not all IgG3 molecules. Little is known about the structural basis of murine IgG3 self-association. A region of the CH3 domain that is unique to IgG3 antibodies is the presence of an extra glycosylation site at residues 471-473. It is known that glycosylation greatly influences solubility. It has also been shown by X-ray crystallography that glycosylated residues (specifically sialic acid) are influential in the contacts of the CH1 to CH2 as well as the CH2 to CH2 domains in a human IgG1 antibody. These findings provided evidence that a direct interaction exists between the glycosylated residues and other residues within the constant and/or variable domains. It was, therefore, important to determine whether the glycosylated residue in the CH3 domain of the IgG3 constant region is influential in self-association. We have found that removing the glycosylation site by site-directed mutagenesis of an IgG3 RF significantly reduced the self-associating ability of this antibody.
Panka
D J
DJ
Department of Microbiology, Boston University Medical School, MA 02118, U.S.A.
D000818:Animals; D003001:Cloning, Molecular; D006031:Glycosylation; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry* / Q000235:genetics; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D051379:Mice; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D012217:Rheumatoid Factor / Q000276:immunology*
D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D012217:Rheumatoid Factor