The paradigmatic DNA binding domain from the transcription factor Zif2
68 contains three zinc finger modules in tandem repeat. When bound to
their cognate DNA site the fingers read out the sequence of one DMA st
rand by making a linear series of successive base contacts, It is show
n that the base-specific protein-DNA contacts made from the ends of th
e Zif268 three-finger array contribute less to the stability of the in
termolecular complex than do structurally equivalent contacts from mor
e central regions of the DNA binding domain, The effect is akin to the
end fraying observed in duplex nucleic acid molecules.