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Red fluorescent protein eqFP611 and its genetically engineered dimeric variants.
Jörg Wiedenmann1, Beatrice Vallone, Fabiana Renzi
1University of Ulm, Department of Zoology and Endocrinology, 89069 Ulm, Germany. joerg.wiedenmann@biologie.uni-ulm.de
Journal of Biomedical Optics
|April 26, 2005
Summary
Researchers engineered monomeric fluorescent proteins (FPs) from eqFP611 by altering its tetrameric interfaces. This study provides a foundation for developing novel monomeric FPs for molecular marking applications.
Area of Science:
- Structural biology
- Biochemistry
- Molecular biology
Background:
- The red fluorescent protein (FP) eqFP611 from Entacmaea quadricolor exhibits properties suitable for molecular markers.
- Anthozoan FPs, including eqFP611, typically form tetramers at physiological concentrations, but eqFP611 shows weak inter-monomer interactions.
- Monomeric FPs are preferred for fusion markers due to their enhanced utility and reduced potential for aggregation.
Purpose of the Study:
- To investigate the structural basis of weak subunit interactions in the tetrameric eqFP611.
- To identify and engineer monomeric variants of eqFP611 for improved molecular marker applications.
- To understand the role of specific interfaces in the folding and function of eqFP611.
Main Methods:
- X-ray crystallography was used to determine the structure of tetrameric eqFP611.
- Single-molecule fluorescence analysis was employed to assess monomeric fluorescence.
- Site-directed mutagenesis was performed to introduce point mutations at specific interfacial sites (A/B and A/C).
Main Results:
- The crystal structure revealed a tetrameric arrangement of beta-cans, similar to other green fluorescent protein (GFP)-like proteins.
- Specific structural features at the tetrameric interfaces were identified as contributing to weak subunit interactions.
- Mutations in the A/B interface yielded functional dimeric variants, while modifications in the A/C interface abolished fluorescence, indicating its critical role in protein folding.
Conclusions:
- Weak inter-subunit interactions in eqFP611 are attributed to specific structural features at its tetrameric interfaces.
- Targeted mutations at the A/B interface can produce functional dimeric fluorescent proteins.
- The A/C interface is crucial for the proper folding and functional integrity of eqFP611, highlighting its importance for protein stability and fluorescence.