7UQA image
Deposition Date 2022-04-19
Release Date 2023-07-19
Last Version Date 2023-10-25
Entry Detail
PDB ID:
7UQA
Title:
Crystal structure of the small Ultra-Red Fluorescent Protein (smURFP)
Biological Source:
Source Organism:
Host Organism:
Method Details:
Experimental Method:
Resolution:
2.80 Å
R-Value Free:
0.26
R-Value Work:
0.23
R-Value Observed:
0.24
Space Group:
C 2 2 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:small Ultra-Red Fluorescent Protein (smURFP)
Chain IDs:A, B, C, D, E, F
Chain Length:140
Number of Molecules:6
Biological Source:synthetic construct
Primary Citation
Structural and photophysical characterization of the small ultra-red fluorescent protein.
Nat Commun 14 4155 4155 (2023)
PMID: 37438348 DOI: 10.1038/s41467-023-39776-9

Abstact

The small Ultra-Red Fluorescent Protein (smURFP) represents a new class of fluorescent protein with exceptional photostability and brightness derived from allophycocyanin in a previous directed evolution. Here, we report the smURFP crystal structure to better understand properties and enable further engineering of improved variants. We compare this structure to the structures of allophycocyanin and smURFP mutants to identify the structural origins of the molecular brightness. We then use a structure-guided approach to develop monomeric smURFP variants that fluoresce with phycocyanobilin but not biliverdin. Furthermore, we measure smURFP photophysical properties necessary for advanced imaging modalities, such as those relevant for two-photon, fluorescence lifetime, and single-molecule imaging. We observe that smURFP has the largest two-photon cross-section measured for a fluorescent protein, and that it produces more photons than organic dyes. Altogether, this study expands our understanding of the smURFP, which will inform future engineering toward optimal FPs compatible with whole organism studies.

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