Engrailed (Gln50-->Lys) homeodomain-DNA complex at 1.9 A resolution: structural basis for enhanced affinity and altered specificity.
Tucker-Kellogg, L., Rould, M.A., Chambers, K.A., Ades, S.E., Sauer, R.T., Pabo, C.O.(1997) Structure 5: 1047-1054
- PubMed: 9309220 
- DOI: https://doi.org/10.1016/s0969-2126(97)00256-6
- Primary Citation of Related Structures:  
2HDD - PubMed Abstract: 
The homeodomain is one of the key DNA-binding motifs used in eukaryotic gene regulation, and homeodomain proteins play critical roles in development. The residue at position 50 of many homeodomains appears to determine the differential DNA-binding specificity, helping to distinguish among binding sites of the form TAATNN. However, the precise role(s) of residue 50 in the differential recognition of alternative sites has not been clear. None of the previously determined structures of homeodomain-DNA complexes has shown evidence for a stable hydrogen bond between residue 50 and a base, and there has been much discussion, based in part on NMR studies, about the potential importance of water-mediated contacts. This study was initiated to help clarify some of these issues.
Organizational Affiliation: 
Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge 02139, USA.