An unlocking/relocking barrier in conformational fluctuations of villin headpiece subdomain.

ABSTRACT: A reversible structural unlocking reaction, in which the close-packed van der Waals interactions break cooperatively, has been found for the villin headpiece subdomain (HP35) using triplet-triplet-energy transfer to monitor conformational fluctuations from equilibrium. Unlocking is associated with an unfavorable enthalpy change (DeltaH(0) = 35 +/- 4 kJ/mol) which is nearly compensated in free energy by the entropy change (DeltaS(0) = 112 +/- 20 Jxmol(-1)xK(-1)). The unlocking reaction has a time constant of about 1 mus at 5 degrees C and is enthalpy-limited with an activation energy of 32 +/- 1 kJ/mol and a large Arrhenius preexponential factor of A = 7.5 x 10(11) s(-1). In the unlocked state a fast local conformational fluctuation with a time constant of 170 ns and a low activation barrie

SUBMITTER: Reiner A 

PROVIDER: S-EPMC2841885 | biostudies-literature | 2010 Mar

REPOSITORIES: biostudies-literature