GFPlike

GFPlike is a general term used to describe a family of fluorescent proteins that resemble green fluorescent protein (GFP) in structure and function. GFPlike proteins typically form a beta-barrel structure that houses an intrinsic chromophore generated from the amino-acid sequence, and emit fluorescence without requiring external cofactors.

The GFPlike family originated with GFP from the jellyfish Aequorea victoria, and has expanded to numerous GFP-like variants from corals and other organisms. These proteins share a conserved chromophore-forming motif and a similar beta-barrel fold, but differ in color, brightness, maturation time, and environmental sensitivity.

Spectral properties and maturation: GFPlike variants cover a range from blue to far-red, depending on mutations; excitation/emission wavelengths, quantum yield, and maturation rates vary; many are engineered to be monomeric to reduce artificial interactions.

Applications: used as fluorescent reporters for gene expression, promoter activity, protein localization, protein-protein interactions (via FRET), and as genetically encoded calcium or pH indicators in live cells.

Limitations and considerations: photobleaching, phototoxicity, pH dependence, brightness limitations, spectral overlap; some variants tend to dimerize or aggregate; proper calibration and exposure control are necessary; tissue autofluorescence can affect imaging.

Variants and development: ongoing protein engineering improves brightness, maturation, and photostability; near-infrared GFPlike proteins enable deeper tissue imaging; ongoing efforts focus on reducing maturation time and improving compatibility with mammalian expression.

See also: GFP, fluorescent protein, chromophore, FRET, live-cell imaging.