Disulfide bond structures of IgG molecules

Microheterogeneity of Recombinant Antibodies: Analytics and Functional Impact

“…The typical disulfide bond arrangements for all four subclasses of IgG has first been described in the 1960s by Milstein et al [85] The most widely known is probably the disulfide bond structure of IgG 1 as depicted in Figure 1 with 12 intrachain disulfide bridges, one interchain bond between the heavy and the light chain of the Fab fragment, and two additional interchain linkages located in the hinge region. The classical structures of the other IgG subclasses differ substantially from this one in the location of the two cysteine residues keeping the Fab fragment connected and in the number of disulfide bridges in the hinge region (two for IgG 1 and IgG 4 , four for IgG 2, and eleven for IgG 3 ).…”

“…For IgG1 the disulfide bridge in the Fab fragment is formed by the last two cysteines in both the heavy and the light chain, whereas for IgG 2 , IgG 3, and IgG 4 the last cysteine residue of the light chain is linked to the fifth cysteine in the heavy chain. [85] As these disulfide bridges form the only covalent linkage between different parts of the polypeptide chain, it can reasonably be expected that they play an essential role for the correct folding and the structural stability of an IgG molecule. Any variations in these disulfide connections therefore deserve special consideration.…”

“…[85] For both subclasses the isoforms observed in MS analysis resulted from variations in the interchain connections between cysteins located in the Fab fragment and in the hinge region. For IgG2, three possible variants have been reported, with one being described as a structural intermediate between the other two.…”

“…[85] The extent to which this incomplete disulfide bridge formation occurs seems to be largely dependent on external conditions. For example, it was possible to reduce the level of free SH groups present in a given antibody by adding copper sulfate to the cell culture.…”

“…[95] Additionally, it seems as if lacking disulfide bridges can be repaired to a certain extent in vivo, which becomes apparent when analyzing antibodies that had been incubated in serum as well as with samples recovered from rat serum after previous administration. [74] Based on the highly reactive chemical nature of free thiol groups, it has been proposed that free sulfhydryls in antibodies www.advancedsciencenews.com www.biotechnology-journal.com might promote the formation of dimers, [85] which could impact the safety of a therapeutic antibody.…”