2p81

OverviewOverview

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.

About this StructureAbout this Structure

2P81 is a Single protein structure of sequence from Drosophila melanogaster. Full crystallographic information is available from OCA.

ReferenceReference

The helix-turn-helix motif as an ultrafast independently folding domain: The pathway of folding of Engrailed homeodomain., Religa TL, Johnson CM, Vu DM, Brewer SH, Dyer RB, Fersht AR, Proc Natl Acad Sci U S A. 2007 May 29;104(22):9272-7. Epub 2007 May 18. PMID:17517666

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