Role of a conserved salt bridge between the PAS core and the N-terminal domain in the activation of the photoreceptor photoactive yellow protein.

ABSTRACT: The effect of ionic strength on the conformational equilibrium between the I(2) intermediate and the signaling state I(2)' of the photoreceptor PYP and on the rate of recovery to the dark state were investigated by time-resolved absorption and fluorescence spectroscopy. With increasing salt concentration up to approximately 600 mM, the recovery rate k(3) decreases and the I(2)/I(2)' equilibrium (K) shifts in the direction of I(2)'. At higher ionic strength both effects reverse. Experiments with mono-(KCl, NaBr) and divalent (MgCl(2), MgSO(4)) salts show that the low salt effect depends on the ionic strength and not on the cation or anion species. These observations can be described over the entire ionic strength range by considering the activity coefficients of an interdomain salt bridge.

SUBMITTER: Hoersch D 

PROVIDER: S-EPMC1948051 | biostudies-literature | 2007 Sep

REPOSITORIES: biostudies-literature