Zipperless bZips and Zipped Homeodomains

Abstract

DNA recognition of zipperless basic-zipper (bZip) proteins and zipped homeodomains (HDs) are discussed in the light of the structure and the DNA-binding specificity of ordinary bZip and HD proteins. Proteins, Mastermind, Skin-1 and Srg-1, have twelve residue sequences which are very similar to that of the basic domain but lack the “zipper” sequences, which follows the basic domain in bZip proteins. It is predicted here that these proteins and Zeste and RAP1 have a domain which is composed of three α-helices as in an HD and the proteins bind to the DNA by a recognition helix of the HD-bZip type.