Functional antibody lacking a variable-region disulfide bridge.

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Abstract
In 1981, Auffray et al. [Auffray, C., Sikorav. J.L., Ollo, R. and Rougeon, F. (1985) Ann. Immunol. (Inst. Pasteur) 132D, 77-88] reported a partial cDNA sequence of the heavy chain from the ABPC48 plasmacytoma whose protein product has previously been shown to bind bacterial and grass levan. In the cDNA sequence the second half-cysteine of the heretofore invariant disulfide bridge had been replaced by a tyrosine. Since the presence of invariant variable-region disulfide bridges has been considered a basic structural feature of the antibody molecule necessary for proper folding and function, we have analyzed the heavy chain protein produced by ABPC48. Our results indicate that heavy chains from ABPC48 quantitatively express tyrosine in place of the normally occurring second half-cystine in the variable region. Furthermore, this antibody populations capable of both binding antigen and subsequent precipitation. Thus, the presence of a disulfide bridge in the heavy-chain variable region does not appear necessary for proper function of this antibody and may not be obligatory for antibody function in general, as has been assumed previously.