LifeAct

LifeAct is a short peptide used as a fluorescent probe to visualize filamentous actin (F-actin) in living cells. Derived from the actin-binding region of the yeast protein Abp140, the peptide comprises about 17 amino acids. When fused to fluorescent proteins such as GFP or mCherry, LifeAct enables real-time imaging of actin dynamics as LifeAct-GFP or LifeAct-mCherry.

LifeAct binds along the length of F-actin filaments, labeling cortical networks, lamellipodia, filopodia, and stress fibers, depending on cell type and state. It is widely used for imaging in cultured cells and in model organisms, including Drosophila, C. elegans, zebrafish, and plants, using standard fluorescence microscopy.

Advantages include its small size, which tends to perturb actin less than larger actin-binding domains and its suitability for live-cell imaging. Nevertheless, LifeAct can alter actin dynamics or morphology at high expression levels and its labeling can vary with the cellular context and coexpressed actin-binding proteins. It may not equally report all actin structures and can exhibit off-target or misleading localization in some systems, making appropriate controls important.

Variants and controls: Researchers often express LifeAct at low levels, use nonbinding mutants as controls, or compare with alternative probes such as utrophin-CH or other F-actin reporters to validate observations.

Origin: LifeAct was developed in the late 2000s by Riedl and colleagues as a compact F-actin marker for live-cell imaging.