SPECIFIC CLEAVAGE OF IMMUNOGLOBULIN-G BY COPPER IONS

The hinge region of a recombinant-DNA-produced human IgG(1) (Campath 1 H(TM)) is specifically cleavable at a single copper-sensitive peptide bond, yielding a distinct fragment resolved by size-exclusion high-per formance liquid chromatography. This novel metal ion-catalysed cleavag e at slightly alkaline pH is inhibited by EDTA and its rate is reduced at slightly acidic conditions (pH 5-6) and accelerated by increasing concentrations of cupric ion and higher temperature. Complete cleavage was observed after incubation at pH 8 for 24 h with 1 mM CuCl2. Seque nce analysis determined the cleavage site to be the Lys(226)-Thr(227) bond in the hinge-region sequence DKTHT. Cleavage of other IgGs was ob served to varying degrees, and specific cleavage of synthetic peptides containing this pentapeptide sequence was also observed. (C) Munksgaa rd 1996.