Photoactivation of the photoactive yellow protein: why photon absorption triggers a trans-to-cis Isomerization of the chromophore in the protein.
Atomistic QM/MM simulations have been carried out on the complete photocycle of Photoactive Yellow Protein, a bacterial photoreceptor, in which blue light triggers isomerization of a covalently bound chromophore. The "chemical role" of the protein cavity in the control of the photoisomerization step has been elucidated. Isomerization is facilitated due to preferential electrostatic stabilization of the chromophore's excited state by the guanidium group of Arg52, located just above the negatively charged chromophore ring. In vacuo isomerization does not occur. Isomerization of the double bond is enhanced relative to isomerization of a single bond due to the steric interactions between the phenyl ring of the chromophore and the side chains of Arg52 and Phe62. In the isomerized configuration (ground-state cis), a proton transfer from Glu46 to the chromophore is far more probable than in the initial configuration (ground-state trans). It is this proton transfer that initiates the conformational changes within the protein, which are believed to lead to signaling.
Groenhof
Gerrit
G
Department of Biophysical Chemistry, University of Groningen, Nijenborg 4, 9747 AG Groningen, The Netherlands.
Bouxin-Cademartory
Mathieu
M
Hess
Berk
B
De Visser
Sam P
SP
Berendsen
Herman J C
HJ
Olivucci
Massimo
M
Mark
Alan E
AE
Robb
Michael A
MA
D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D003373:Coumaric Acids / Q000737:chemistry; D004952:Esters / Q000737:chemistry; D007536:Isomerism; D010777:Photochemistry; D017785:Photons; D020283:Photoreceptors, Microbial / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D011487:Protein Conformation; D015398:Signal Transduction; D013438:Sulfhydryl Compounds / Q000737:chemistry
D001426:Bacterial Proteins; D003373:Coumaric Acids; D004952:Esters; D020283:Photoreceptors, Microbial; D013438:Sulfhydryl Compounds; C050162:photoactive yellow protein, Bacteria