Phi-Yellow fluorescent proteins

- Bright yellow fluorescence
- Proven suitability to generate stably transfected cell lines
- Destabilized variant is available

Available variants and fusions

PhiYFP: PhiYFP codon usage is optimized for high expression in mammalian cells [Haas et al., 1996], but it can be successfully expressed in many other heterological systems. PhiYFP allows generation of fusions to its N-terminus but unsuited to generate C-terminal fusions.

PhiYFP-m variant: PhiYFP-m variant is a mutant of PhiYFP. It is suitable for fusion generation to its C-terminus.

PhiYFP-mito fusion: A mitochondrial targeting sequence (MTS) is linked to the PhiYFP N-terminus. MTS was derived from the subunit VIII of human cytochrome C oxidase [Rizzuto et al., 1989; Rizzuto et al., 1995]. When expressed in mammalian cells, this variant provides green fluorescent labeling of mitochondria.

PhiYFP-m-peroxi fusion: Peroximal targeting signal [Gould et al., 1989] encoding tripeptide SKL was fused to the 3' end of PhiYFP-m sequence. This tripeptide targets the fusion protein to the matrix of peroxisomes.

Destabilized PhiYFP-m variant (PhiYFP-m-dest1): PhiYFP-m-dest1 is produced by fusing the initial protein with PEST amino acid sequence encoded by region 422-461 of mouse ornithine decarboxylase gene [Li et al., 1998]. This sequence targets the protein to degradation and enables a rapid protein turnover.
PhiYFP-m-dest1 retains spectral properties of the initial protein, but has shorter half-lives (approximately 2 hrs) as measured by the analysis of fluorescence intensity of cells treated with a protein synthesis inhibitor, cycloheximide. Because of rapid turnover, PhiYFP-m-dest1 can be used to measure changes in gene expression.

Fluorescence intensities of cells expressing PhiYFP-m-dest1 rapidly decrease in response to cycloheximide (CHX). Mammalian cells expressing PhiYFP-mP-dest1 under the control of CMV promoter were treated with CHX. After 1.5 hours CHX treatment, fluorescence intensity of cells was greatly reduced.