Heparin-binding EGF-like growth factor (HB-EGF) is a member of the EGF family of proteins. It has been shown to play a role in wound healing, cardiac hypertrophy and heart development and function.

Diphtheria toxin inhibits protein synthesis in eukaryotic cells by catalyzing inactivation of elongation factor-2 (EF2). Entry of toxin into cells is dependent on binding to the cell surface.

Mice and rats are resistant to diphtheria toxin, and the resistance extends to cultured cells. Mouse-human hybrid cells are sensitive to diphtheria toxin. Creagan et al. (1975) showed that sensitivity is determined by human chromosome 5, which presumably carries a gene for a receptor for toxin.