Conserved tyrosine in phytochromes controls the photodynamics through steric demand and hydrogen bonding capabilities.
Biochim Biophys Acta Bioenerg
; 1864(4): 148996, 2023 11 01.
Article
em En
| MEDLINE
| ID: mdl-37437858
ABSTRACT
Using ultrafast spectroscopy and site-specific mutagenesis, we demonstrate the central role of a conserved tyrosine within the chromophore binding pocket in the forward (Pr â Pfr) photoconversion of phytochromes. Taking GAF1 of the knotless phytochrome All2699g1 from Nostoc as representative member of phytochromes, it was found that the mutations have no influence on the early (<30 ps) dynamics associated with conformational changes of the chromophore in the excited state. Conversely, they drastically impact the extended protein-controlled excited state decay (>100 ps). Thus, the steric demand, position and H-bonding capabilities of the identified tyrosine control the chromophore photoisomerization while leaving the excited state chromophore dynamics unaffected. In effect, this residue operates as an isomerization-steric-gate that tunes the excited state lifetime and the photoreaction efficiency by modulating the available space of the chromophore and by stabilizing the primary intermediate Lumi-R. Understanding the role of such a conserved structural element sheds light on a key aspect of phytochrome functionality and provides a basis for rational design of optimized photoreceptors for biotechnological applications.
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MEDLINE
Assunto principal:
Fitocromo
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Fenômenos Bioquímicos
Idioma:
En
Ano de publicação:
2023
Tipo de documento:
Article