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Spectroscopic properties of the carotenoid 3 '-hydroxyechinenone in the orange carotenoid protein from the cyanobacterium Arthrospira maxima

Polivka, Tomas LU ; Kerfeld, C A; Pascher, Torbjörn LU and Sundström, Villy LU (2005) In Biochemistry 44(10). p.3994-4003
Abstract
The cyanobacterial water-soluble orange carotenoid binding protein (OCP) is an ideal system for study of the effects of protein environment on photophysical properties of carotenoids. It contains a single pigment, the carotenoid 3'-hydoxyechinenone (hECN). In this study, we focus on spectroscopic properties of hECN in solution and in the OCP, aiming to elucidate the spectroscopic effects of the carotenoid-protein interaction in the context of the function(s) of the OCP. The noncovalent binding of hECN to the OCP causes a conformational change in the hECN, leading to a prolongation of the effective conjugation length. This change is responsible for shortening of the S, lifetime from 6.5 ps in solution to 3.3 ps in the OCP. The... (More)
The cyanobacterial water-soluble orange carotenoid binding protein (OCP) is an ideal system for study of the effects of protein environment on photophysical properties of carotenoids. It contains a single pigment, the carotenoid 3'-hydoxyechinenone (hECN). In this study, we focus on spectroscopic properties of hECN in solution and in the OCP, aiming to elucidate the spectroscopic effects of the carotenoid-protein interaction in the context of the function(s) of the OCP. The noncovalent binding of hECN to the OCP causes a conformational change in the hECN, leading to a prolongation of the effective conjugation length. This change is responsible for shortening of the S, lifetime from 6.5 ps in solution to 3.3 ps in the OCP. The conformational change and the hydrogen bonding via the carbonyl group of hECN result in stabilization of an intramolecular charge-transfer (ICT) state. No signs of the ICT state were found in hECN in solution, regardless of the solvent polarity; spectral bands in transient absorption spectra of OCP-bound hECN exhibit features typical for the ICT state. Application of global fitting analysis revealed further effects of binding hECN in the OCP. The S, state of hECN in the OCP decays with two time constants of 0.9 and 3.3 ps. Modeling of the excited-state processes suggests that these two components are due to two populations of hECN in the OCP that differ in the hydrogen bonding via the carbonyl group. These results support the hypothesis that the OCP functions as a photoprotective shield under excess light. Mechanistically, the broadening of the hECN absorption spectrum upon binding to OCP enhances filtering, effect of hECN. Furthermore, the binding-induced conformational change and activation of the ICT state that leads to a shortening of hECN lifetime effectively makes the protein-bound hECN a more effective energy dissipator. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biochemistry
volume
44
issue
10
pages
3994 - 4003
publisher
The American Chemical Society
external identifiers
  • wos:000227629300034
  • pmid:15751975
  • scopus:14844347730
ISSN
0006-2960
DOI
10.1021/bi047473t
language
English
LU publication?
yes
id
7a5ad917-01f2-4f0a-af58-20c33eab014b (old id 151958)
date added to LUP
2007-07-03 14:49:05
date last changed
2017-11-19 03:38:50
@article{7a5ad917-01f2-4f0a-af58-20c33eab014b,
  abstract     = {The cyanobacterial water-soluble orange carotenoid binding protein (OCP) is an ideal system for study of the effects of protein environment on photophysical properties of carotenoids. It contains a single pigment, the carotenoid 3'-hydoxyechinenone (hECN). In this study, we focus on spectroscopic properties of hECN in solution and in the OCP, aiming to elucidate the spectroscopic effects of the carotenoid-protein interaction in the context of the function(s) of the OCP. The noncovalent binding of hECN to the OCP causes a conformational change in the hECN, leading to a prolongation of the effective conjugation length. This change is responsible for shortening of the S, lifetime from 6.5 ps in solution to 3.3 ps in the OCP. The conformational change and the hydrogen bonding via the carbonyl group of hECN result in stabilization of an intramolecular charge-transfer (ICT) state. No signs of the ICT state were found in hECN in solution, regardless of the solvent polarity; spectral bands in transient absorption spectra of OCP-bound hECN exhibit features typical for the ICT state. Application of global fitting analysis revealed further effects of binding hECN in the OCP. The S, state of hECN in the OCP decays with two time constants of 0.9 and 3.3 ps. Modeling of the excited-state processes suggests that these two components are due to two populations of hECN in the OCP that differ in the hydrogen bonding via the carbonyl group. These results support the hypothesis that the OCP functions as a photoprotective shield under excess light. Mechanistically, the broadening of the hECN absorption spectrum upon binding to OCP enhances filtering, effect of hECN. Furthermore, the binding-induced conformational change and activation of the ICT state that leads to a shortening of hECN lifetime effectively makes the protein-bound hECN a more effective energy dissipator.},
  author       = {Polivka, Tomas and Kerfeld, C A and Pascher, Torbjörn and Sundström, Villy},
  issn         = {0006-2960},
  language     = {eng},
  number       = {10},
  pages        = {3994--4003},
  publisher    = {The American Chemical Society},
  series       = {Biochemistry},
  title        = {Spectroscopic properties of the carotenoid 3 '-hydroxyechinenone in the orange carotenoid protein from the cyanobacterium Arthrospira maxima},
  url          = {http://dx.doi.org/10.1021/bi047473t},
  volume       = {44},
  year         = {2005},
}