The role of the N-terminal domain of photoactive yellow protein in the transient partial unfolding during signalling state formation

It is shown that the N-terminal domain of photoactive yellow protein (PYP), which appears relatively independently folded in the ground state of the p rotein. plays a key role in the transient unfolding during signalling state formation: genetic truncation of the N-terminal domain of PYP significantl y decreases the extent of cooperativity of the titration curve that describ es chromophore protonation in the ground state of PYP, which is in agreemen t with the notion that the N-terminal domain is linked through a hydrogen-b onding network with the chromophore-containing domain of the protein. Furth ermore, deletion of the N-terminal domain completely abolishes the nonlinea rity of the Arrhenius plot of the rate of ground state recovery. (C) 2001 P ublished by Elsevier Science B.V. on behalf of the Federation of European B iochemical Societies.