NMR unfolding studies on a liver bile acid binding protein reveal a global two-state unfolding and localized singular behaviors.
The folding properties of a bile acid binding protein, belonging to a subfamily of the fatty acid binding proteins, have been here investigated both by hydrogen exchange measurements, using the SOFAST NMR approach, and urea denaturation experiments. The urea unfolding profiles of individual residues, acting as single probes, were simultaneously analyzed through a global fit, according to a two-state unfolding model. The resulting conformational stability DeltaG(U)(H(2)O)=7.2+/-0.25kcal mol(-1) is in good agreement with hydrogen exchange stability DeltaG(op). While the majority of protein residues satisfy this model, few amino-acids display a singular behavior, not directly amenable to the presence of a folding intermediate, as reported for other fatty acid binding proteins. These residues are part of a protein patch characterized by enhanced plasticity. To explain this singular behavior a tentative model has been proposed which takes into account the interplay between the dynamic features and the formation of transient aggregates. A functional role for this plasticity, related to translocation across the nuclear membrane, is discussed.
D'Onofrio
Mariapina
M
Dipartimento Scientifico e Tecnologico, Strada le Grazie 15, Università degli Studi di Verona, Verona, Italy.
Ragona
Laura
L
Fessas
Dimitrios
D
Signorelli
Marco
M
Ugolini
Raffaella
R
Pedò
Massimo
M
Assfalg
Michael
M
Molinari
Henriette
H
D002352:Carrier Proteins / Q000737:chemistry*; D008562:Membrane Glycoproteins / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; C037643:bile acid binding proteins