2q57
From Proteopedia
(New page: 200px<br /><applet load="2q57" size="350" color="white" frame="true" align="right" spinBox="true" caption="2q57, resolution 2.00Å" /> '''X-ray structure of C...) |
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==Overview== | ==Overview== | ||
| - | The crystal structure of the cyan-fluorescent Cerulean green fluorescent | + | The crystal structure of the cyan-fluorescent Cerulean green fluorescent protein (GFP), a variant of enhanced cyan fluorescent protein (ECFP), has been determined to 2.0 A. Cerulean bears an internal fluorophore composed of an indole moiety derived from Y66W, conjugated to the GFP-like imidazolinone ring via a methylene bridge. Cerulean undergoes highly efficient fluorescence resonance energy transfer (FRET) to yellow acceptor molecules and exhibits significantly reduced excited-state heterogeneity. This feature was rationally engineered in ECFP by substituting His148 with an aspartic acid [Rizzo et al. (2004) Nat. Biotechnol. 22, 445], rendering Cerulean useful for fluorescence lifetime imaging microscopy (FLIM). The X-ray structure is consistent with a single conformation of the chromophore and surrounding residues and may therefore provide a structural rationale for the previously described monoexponential fluorescence decay. Unexpectedly, the carboxyl group of H148D is found in a buried position, directly contacting the indole nitrogen of the chromophore via a bifurcated hydrogen bond. Compared to the similarly constructed ECFP chromophore, the indole group of Cerulean is rotated around the methylene bridge to adopt a cis-coplanar conformation with respect to the imidazolinone ring, resulting in a close edge-to-edge contact of the two ring systems. The double-humped absorbance spectrum persists in single-crystal absorbance measurements, casting doubt on the idea that ground state conformational heterogeneity forms the basis of the two overlapping transitions. At low pH, a blue shift in absorbance of 10-15 nm suggests a pH-induced structural transition that proceeds with a time constant of 47 (+/-2) min and is reversible. Possible interpretations in terms of chromophore isomerization are presented. |
==About this Structure== | ==About this Structure== | ||
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[[Category: Aequorea victoria]] | [[Category: Aequorea victoria]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Malo, G | + | [[Category: Malo, G D.]] |
[[Category: beta barrel]] | [[Category: beta barrel]] | ||
[[Category: fluorescent protein]] | [[Category: fluorescent protein]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 18:36:13 2008'' |
Revision as of 16:36, 21 February 2008
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X-ray structure of Cerulean GFP: A tryptophan-based chromophore useful for fluorescence lifetime imaging
Overview
The crystal structure of the cyan-fluorescent Cerulean green fluorescent protein (GFP), a variant of enhanced cyan fluorescent protein (ECFP), has been determined to 2.0 A. Cerulean bears an internal fluorophore composed of an indole moiety derived from Y66W, conjugated to the GFP-like imidazolinone ring via a methylene bridge. Cerulean undergoes highly efficient fluorescence resonance energy transfer (FRET) to yellow acceptor molecules and exhibits significantly reduced excited-state heterogeneity. This feature was rationally engineered in ECFP by substituting His148 with an aspartic acid [Rizzo et al. (2004) Nat. Biotechnol. 22, 445], rendering Cerulean useful for fluorescence lifetime imaging microscopy (FLIM). The X-ray structure is consistent with a single conformation of the chromophore and surrounding residues and may therefore provide a structural rationale for the previously described monoexponential fluorescence decay. Unexpectedly, the carboxyl group of H148D is found in a buried position, directly contacting the indole nitrogen of the chromophore via a bifurcated hydrogen bond. Compared to the similarly constructed ECFP chromophore, the indole group of Cerulean is rotated around the methylene bridge to adopt a cis-coplanar conformation with respect to the imidazolinone ring, resulting in a close edge-to-edge contact of the two ring systems. The double-humped absorbance spectrum persists in single-crystal absorbance measurements, casting doubt on the idea that ground state conformational heterogeneity forms the basis of the two overlapping transitions. At low pH, a blue shift in absorbance of 10-15 nm suggests a pH-induced structural transition that proceeds with a time constant of 47 (+/-2) min and is reversible. Possible interpretations in terms of chromophore isomerization are presented.
About this Structure
2Q57 is a Single protein structure of sequence from Aequorea victoria. Full crystallographic information is available from OCA.
Reference
X-ray structure of Cerulean GFP: a tryptophan-based chromophore useful for fluorescence lifetime imaging., Malo GD, Pouwels LJ, Wang M, Weichsel A, Montfort WR, Rizzo MA, Piston DW, Wachter RM, Biochemistry. 2007 Sep 4;46(35):9865-73. Epub 2007 Aug 8. PMID:17685554
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