The helix-turn-helix motif as an ultrafast independently folding domain: the pathway of folding of Engrailed homeodomain.

ABSTRACT: 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 stepwi

SUBMITTER: Religa TL 

PROVIDER: S-EPMC1890484 | biostudies-literature | 2007 May

REPOSITORIES: biostudies-literature