ABSTRACT
Many procaryotic transcription factors are dimers that recognize palindromic DNA sequences in such a way that each subunit binds one half-site. Dimerization and DNA-binding activities usually reside in different domains or regions of the protein, as was discussed in Chapter 8. The POU transcription factors exhibit a variation of this theme by having two similar domains in one polypeptide chain (see Chapter 9). A similar arrangement is found in another important class of specific eucaryotic transcription factors-those that have zinc atoms in their DNA-binding motifs. As we will see, the polypeptide chains of these proteins may contain several homologous domains, each capable of specific DNA binding and each containing zinc as an integral part of the DNA-binding domain. These proteins belong to several different groups with different structures and different modes of DNA binding. We will discuss three of them that illustrate three different ways by which zinc-containing motifs recognize specific binding sites arranged contiguously along DNA segments.
