A structural basis for the pH-dependent increase in fluorescence efficiency of chromoproteins

Battad, J. M., Wilmann, P. G., Olsen, S. C., Byres, E., Smith, S. C., Dove, S. G., Turcic, K. N., Devenish, R. J., Rossjohn, J. and Prescott, M. (2007) A structural basis for the pH-dependent increase in fluorescence efficiency of chromoproteins. Journal of Molecular Biology, 368 4: 998-1010.


Author Battad, J. M.
Wilmann, P. G.
Olsen, S. C.
Byres, E.
Smith, S. C.
Dove, S. G.
Turcic, K. N.
Devenish, R. J.
Rossjohn, J.
Prescott, M.
Title A structural basis for the pH-dependent increase in fluorescence efficiency of chromoproteins
Journal name Journal of Molecular Biology   Check publisher's open access policy
ISSN 0022-2836
Publication date 2007-05-11
Sub-type Article (original research)
DOI 10.1016/j.jmb.2007.02.007
Volume 368
Issue 4
Start page 998
End page 1010
Total pages 13
Place of publication London
Publisher Academic Press Ltd Elsevier Science Ltd
Collection year 2008
Language eng
Subject 259999 Chemical Sciences not elsewhere classified
C1
780103 Chemical sciences
Abstract Within the fluorescent protein and chromoprotein family, the phenomenon of photoswitching is both intriguing and biotechnologically useful. Illumination of particular chromoproteins with intense light results in dramatic increases in fluorescence efficiency (termed kindling) and involves cis-trans isomerization of the chromophore. Here we report that chromophore isomerization can also be driven via alteration in pH. Specifically, we demonstrate that a number of naturally occurring chromoproteins, and their engineered variants, undergo a dramatic 20-100-fold increase in fluorescence efficiency at alkaline pH (> pH9.0). We have determined to 1.8 A resolution the structure of one such chromoprotein, Rtms5(H146S), in its highly far-red fluorescent form (Phi(F), 0.11 at pH 10.7) and compared it to the structure of the non-fluorescent form (Phi(F), 0.002, at pH 8.0). At high pH, the cyclic tri-peptide chromophore was observed to be mobile and distributed between a trans non-coplanar and a cis coplanar conformation, whereas at the lower pH, only a trans non-coplanar chromophore was observed. Calculation of pK(a) values suggested that titration of the side-chain of the conserved Glu215 close to the chromophore is involved in promoting the cis-coplanar conformation. Collectively, our data establish that isomerization to form a coplanar chromophore is a basis of the increased fluorescence efficiency at high pH. The phenomenon of pH-induced fluorescence gain has similarities with photoswitching, thereby providing a model to study the mechanism of kindling. (c) 2007 Elsevier Ltd. All rights reserved.
Keyword Biochemistry & Molecular Biology
Rtms5
Chromoprotein
Structure
Fluorescence
Chromophore Configuration
Molecular-orbital Methods
Gfp-like Proteins
Crystal-structure
Entacmaea-quadricolor
Pocilloporin Pigment
Dielectric-constants
Blue Chromoprotein
Basis Sets
Chromophore
Red
Q-Index Code C1
Q-Index Status Confirmed Code

 
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Created: Mon, 18 Feb 2008, 17:08:08 EST