Title of article :
Partially Unfolded Forms and Non-two-state Folding of a β-Sandwich: FHA Domain from Arabidopsis Receptor Kinase-associated Protein Phosphatase
Author/Authors :
Xiangyang Liang، نويسنده , , Gui-in Lee، نويسنده , , Steven R. Van Doren، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2006
Abstract :
FHA domains adopt a β-sandwich fold with 11 strands. The first evidence of partially unfolded forms of a β-sandwich is derived from native-state hydrogen exchange (NHX) of the forkhead-associated (FHA) domain from kinase-associated protein phosphatase from Arabidopsis. The folding kinetics of this FHA domain indicate that EX2 behavior prevails at pH 6.3. In the chevron plot, rollover in the folding arm and bends in the unfolding arm suggest folding intermediates. NHX of this FHA domain suggests a core of six most stable β-strands and two loops, characterized by rare global unfolding events. Flanking this stable core are β-strands and recognition loops with less stability, termed subglobal motifs. These suggest partially unfolded forms (near-native intermediates) with two levels of stability. The spatial separation of the subglobal motifs on the flanks suggests possible parallelism in their folding as additional β-strands align with the stable core of six strands. Intermediates may contribute to differences in stabilities and m-values suggested by NHX or kinetics relative to chemical denaturation. Residual structure in the unfolded regime is suggested by superprotection of β-strand 6 and by GdmCl-dependence of adjustments in amide NMR spectra and residual optical signal. The global folding stability depends strongly on pH, with at least 3 kcal/mol more stability at pH 7.3 than at pH 6.3. This FHA domain is hypothesized to fold progressively with initial hydrophobic collapse of its stable six-stranded core followed by addition of less stable flanking β-strands and ordering of recognition loops.
Keywords :
protein folding intermediates , native-state hydrogen exchange , chevron plot , partially unfolded forms
Journal title :
Journal of Molecular Biology
Journal title :
Journal of Molecular Biology