Volume-conserving trans-cis isomerization pathways in photoactive yellow protein visualized by picosecond X-ray crystallography

Journal Article · Sun Feb 03 00:00:00 EST 2013 · Nature Chemistry

DOI:https://doi.org/10.1038/nchem.1565· OSTI ID:1063643

Jung, Yang Ouk; Lee, Jae Hyuk; Kim, Joonghan; Schmidt, Marius; Moffat, Keith; Šrajer, Vukica; Ihee, Hyotcherl ^[1]

---

1. KAIST-D

Trans-to-cis isomerization, the key reaction in photoactive proteins, usually cannot occur through the standard one-bond-flip mechanism. Owing to spatial constraints imposed by a protein environment, isomerization probably proceeds through a volume-conserving mechanism in which highly choreographed atomic motions are expected, the details of which have not yet been observed directly. Here we employ time-resolved X-ray crystallography to visualize structurally the isomerization of the p-coumaric acid chromophore in photoactive yellow protein with a time resolution of 100 ps and a spatial resolution of 1.6 Å. The structure of the earliest intermediate (I_T) resembles a highly strained transition state in which the torsion angle is located halfway between the trans- and cis-isomers. The reaction trajectory of IT bifurcates into two structurally distinct cis intermediates via hula-twist and bicycle-pedal pathways. The bifurcating reaction pathways can be controlled by weakening the hydrogen bond between the chromophore and an adjacent residue through E46Q mutation, which switches off the bicycle-pedal pathway.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: FOREIGNNSFNIH
• OSTI ID: 1063643
• Journal Information: Nature Chemistry, Vol. 5; ISSN 1755-4330
• Country of Publication: United States
• Language: ENGLISH