Structural studies of the engrailed homeodomain.
The structure of the Drosophila engrailed homeodomain has been solved by molecular replacement and refined to an R-factor of 19.7% at a resolution of 2.1 A. This structure offers a high-resolution view of an important family of DNA-binding proteins and allows comparison to the structure of the same protein bound to DNA. The most significant difference between the current structure and that of the 2.8-A engrailed-DNA complex is the close packing of an extended strand against the rest of the protein in the unbound protein. Structural features of the protein not previously noted include a "herringbone" packing of 4 aromatic residues in the core of the protein and an extensive network of salt bridges that covers much of the helix 1-helix 2 surface. Other features that may play a role in stabilizing the native state include the interaction of buried carbonyl oxygen atoms with the edge of Phe 49 and a bias toward statistically preferred side-chain dihedral angles. There is substantial disorder at both ends of the 61 amino acid protein. A 51-amino acid variant of engrailed (residues 6-56) was synthesized and shown by CD and thermal denaturation studies to be structurally and thermodynamically similar to the full-length domain.
Clarke
N D
ND
Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205.
Kissinger
C R
CR
Desjarlais
J
J
Gilliland
G L
GL
Pabo
C O
CO
D000595:Amino Acid Sequence; D000818:Animals; D003460:Crystallization; D018360:Crystallography, X-Ray; D004247:DNA / Q000378:metabolism; D004330:Drosophila; D029721:Drosophila Proteins; D018398:Homeodomain Proteins / Q000737:chemistry*; D006860:Hydrogen Bonding; D007301:Insect Hormones / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012492:Salts / Q000737:chemistry; D013816:Thermodynamics; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism
D029721:Drosophila Proteins; C063459:En protein, Drosophila; D018398:Homeodomain Proteins; D007301:Insect Hormones; D012492:Salts; D014157:Transcription Factors; D004247:DNA