Click here for a diagram of myohemerythrin , which has this fold. The ligand-binding sites of these proteins occur between the alpha helices. A number of cytokines consist of four alpha helices in a bundle. Also examine Simon Brocklehurst's page on cytokines . Introducing alpha domains which bind DNA DNA-binding domains will be examined in more detail in a later chapter.
Transcription factors have a DNA-binding domain and a domain that activates transcription.
Click here for the structure of the cro repressor from phage 434. Also refer to the GCN4 transcription factor leucine zipper described in the section on coiled coils , by Antti Iivanainen of the Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm. See the page in Section 9 on helix-helix packing .