Fluorescence complementation via EF-hand interactions.

Area of Science:

• Molecular biology
• Biochemistry
• Cell biology

Background:

• Fluorescence complementation is a powerful technique for studying molecular recognition.
• Existing methods rarely address calcium-dependent protein-protein interactions.
• Enhanced green fluorescent protein (EGFP) is a commonly used fluorescent protein.

Purpose of the Study:

• To develop a novel fluorescence complementation assay for detecting calcium-dependent protein-protein interactions.
• To demonstrate the feasibility of intracellular fluorescence complementation using modified EGFP fragments.
• To validate the assay's responsiveness to intracellular calcium level changes.

Main Methods:

• Engineering a modified EGFP (EGFP-T1) with trypsin cleavage sites.
• Fusing complementary EGFP fragments to calcium-binding EF-hand motifs.
• Co-transfecting HeLa cells with plasmids encoding the fused EGFP fragments.
• Inducing intracellular calcium increase using ionomycin.

Main Results:

• The modified EGFP fragments, when fused to EF-hand motifs, reassembled intracellularly to produce strong green fluorescence.
• Intracellular calcium increase led to a significant enhancement of the fluorescence signal.
• The reassembly of EF-hand motifs facilitated chromophore maturation and fluorescence complementation.

Conclusions:

• The developed calcium-dependent fluorescence complementation assay enables monitoring of calcium-triggered protein-protein interactions in living cells.
• This novel approach offers a sensitive tool for studying calcium signaling pathways.
• The intracellular reassembly of EGFP fragments is dependent on the dimerization of EF-hand motifs.