Amino acid sequence and target site preference for macaque CCR5 ZFNs. Full sequences of (A) ZFN-L and (B) ZFN-R are shown. A target site selection assay was performed on (C) ZFN-L and (D) ZFN-R, yielding the indicated position-frequency matrix plot. At each position in the plot, the frequency of the intended target base is shown as a positive value, whereas frequencies of unintended bases are plotted below the x-axis.