2P81 image
Deposition Date 2007-03-21
Release Date 2007-06-12
Last Version Date 2024-05-22
Entry Detail
PDB ID:
2P81
Keywords:
Title:
Engrailed homeodomain helix-turn-helix motif
Biological Source:
Source Organism:
Host Organism:
Method Details:
Experimental Method:
Conformers Calculated:
50
Conformers Submitted:
25
Selection Criteria:
structures with the lowest energy
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:Segmentation polarity homeobox protein engrailed
Gene (Uniprot):en
Mutations:L16A
Chain IDs:A
Chain Length:44
Number of Molecules:1
Biological Source:Drosophila melanogaster
Ligand Molecules
Primary Citation
The helix-turn-helix motif as an ultrafast independently folding domain: The pathway of folding of Engrailed homeodomain.
Proc.Natl.Acad.Sci.Usa 104 9272 9277 (2007)
PMID: 17517666 DOI: 10.1073/pnas.0703434104

Abstact

Helices 2 and 3 of Engrailed homeodomain (EnHD) form a helix-turn-helix (HTH) motif. This common motif is believed not to fold independently, which is the characteristic feature of a motif rather than a domain. But we found that the EnHD HTH motif is monomeric and folded in solution, having essentially the same structure as in full-length protein. It had a sigmoidal thermal denaturation transition. Both native backbone and local tertiary interactions were formed concurrently at 4 x 10(5) s(-1) at 25 degrees C, monitored by IR and fluorescence T-jump kinetics, respectively, the same rate constant as for the fast phase in the folding of EnHD. The HTH motif, thus, is an ultrafast-folding, natural protein domain. Its independent stability and appropriate folding kinetics account for the stepwise folding of EnHD, satisfy fully the criteria for an on-pathway intermediate, and explain the changes in mechanism of folding across the homeodomain family. Experiments on mutated and engineered fragments of the parent protein with different probes allowed the assignment of the observed kinetic phases to specific events to show that EnHD is not an example of one-state downhill folding.

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Primary Citation of related structures