The DNA binding specificity of engrailed homeodomain

摘要: The engrailed gene of Drosophila melanogaster is an integral member the highly complex cascade which results in a fully developed fruitfly. product contains homeodomain responsible for DNA binding via helix-turn-helix motif. crystal structure this 60 amino acid residue domain complexed to analogous structures other homeodomain-DNA complexes, consistent with high degree sequence conservation within both protein and DNA. Despite homology, homeodomains do exhibit distinct preferences certain sequences. Such specificity may be at least partly interactions necessary normal development. Using hydroxyl radical as chemical probe, we have examined complexes Engrailed several sequences determine protein's solution. We find that forms single, specific unique site seen co-crystal structure. In contrast, our probe experiments show was determined by vitro selection also present two possible sites. Modification yield single sites removes ambiguity, different, well-behaved Engrailed-DNA complexes. Our underscore utility defining variety modes interaction proteins can occur solution, but might not apparent