Figure 1: Structure and function of human APOBEC proteins. (a) Schematic representation of APOBEC proteins. The zinc-binding motifs, represented by the catalytic domains (CD) and present in single or double copies, are depicted in green. In the proteins that harbor two CD copies, the N- and C-terminal domains are named CD1 and CD2, respectively. APOBEC proteins are drawn to scale, and the total number of amino acids is shown to the right of each version. The scale bar represents the length of 100 amino acids. (b) The conserved amino acid sequence of the zinc-binding motif is shown; the hydrolytic deamination reaction mediated by these enzymes is shown at the bottom of the figure.