The C terminal domain of DNA Fragmentation factor 45kDa (DFF-C) consists of four alpha-helices, which are folded in a helix-packing arrangement, with alpha-2 and alpha-3 packing against a long C-terminal helix (alpha-4). The main function of this domain is the inhibition of DFF40 by binding to its C-terminal catalytic domain through ionic interactions, thereby inhibiting the fragmentation of DNA in the apoptotic process. In addition to blocking the DNase activity of DFF40, the C-terminal region of DFF45 is also important for the DFF40-specific folding chaperone activity, as demonstrated by the ability of DFF45 to refold DFF40 [1].

1: Solution structure of the DFF-C domain of DFF45/ICAD. A structural basis for the regulation of apoptotic DNA fragmentation. Fukushima K, Kikuchi J, Koshiba S, Kigawa T, Kuroda Y, Yokoyama S; J Mol Biol. 2002;321:317-327. PMID:12144788