Early intermediate of photoactive yellow protein photocycle by picosecond X-ray laue crystallography

Abstract

Picosecond time-resolved structural study of PYP has revealed the motion of early intermediates during signal transduction. The high resolution and quality of the extensively-averaged time-resolved crystallographic data allows us to assign the structural change of chromophore and related residues at picosecond regime. Although the previous studies observed structural changes from nanosecond to second and proposed the chromophore isomerization pathway from nanosecond intermediate ($I_cp$) to pR and pB states which contained `volume-conserving`` rotation, this is the first time to clearly visualize sub-nanosecond structural changes of chromophore and to allow us to propose a novel isomerization mechanism containing both HT process and bicycle pedal model. To confirm this scheme unambiguously, further analysis is required.