Binds non-covalently to an enediyne chromophore which is the cytotoxic and mutagenic component of the antibiotic. The chromophore cleaves duplex DNA site-specifically in a single-stranded manner. The apoprotein cleaves proteins selectively, in particular highly basic histones, with H1 proteins being cleaved the more readily. This protein consists of an immunoglobulin-like seven-stranded antiparallel beta-barrel domain linked to a subdomain composed of two beta-hairpin ribbons. Belongs to the neocarzinostatin family.