What is the Difference Between GFP and YFP

The main difference between GFP and YFP is that GFP exhibits green color upon exposure to light ranges from blue to ultraviolet whereas YFP exhibits yellow color upon exposure to the same light. Furthermore, GFP is originally derived from the jellyfish, Aequorea Victoria while YFP is a genetic mutant of GFP protein.

GFP (green fluorescent protein) and YFP (yellow fluorescent protein) are two types of fluorescent proteins, which exhibit different colors of fluorescent upon the exposure to light ranges from blue to ultraviolet range. However, their applications in molecular biology are the same.

Key Areas Covered

1. What is GFP
     – Definition, Features, Applications
2. What is YFP
     – Definition, Features, Applications
3. What are the Similarities Between GFP and YFP
     – Outline of Common Features
4. What is the Difference Between GFP and YFP
     – Comparison of Key Differences

Key Terms

Fluorescent Proteins, GFP (green fluorescent protein), GFP Derivatives, YFP (yellow fluorescent protein)

What is GFP

GFP (green fluorescent protein) is a bioluminescent polypeptide protein naturally occurs in the jellyfish, Aequorea Victoria, and many other marine organisms. In Aequorea Victoria, it is known as aequorin and emits fluorescence when it gets exposed to ranges from blue to ultraviolet light. That means; GFP completely absorbs blue light (475 nm) or the 395 nm light in the long UV range and emit green light (509 nm).

Figure 1: Aequorea Victoria

The GFP protein contains 238 amino acids and the size of the protein is 26.9 kDa. It folds to form the shape of a beta-barrel. Here, the part of the protein which makes it fluorescent is formed from the conjugation of the main chain atoms, Ser65, Tyr66, and Gly67, forming the highly conjugated, planar p-hydroxybenzylideneimidazolinone chromophore in the presence of oxygen.  The chromophore is packed inside the beta-barrel structure, protecting the chromophore from quenching through paramagnetic oxygen, water dipoles or cis-trans isomerization. Also, the non-covalent interactions of the chromophore with the neighboring molecules enhances its spectral properties.

Figure 2: GFP Structure

Furthermore, GFP is used in molecular biology as a reporter of gene expression, proving the expression of a foreign gene inside the host organism. Also, it can be used to determine the sub-cellular locations where a particular protein is going to be expressed. Here, the protein of interest is fused with GFP and this fusion protein is transformed into the host.

Figure 3: EGFP Expression

However, the major drawback with the wild-type GFP is its reduced effectiveness due to the low efficiency folding at physiological temperatures such as 37 °C, dropping the fluorescent signal. Also, the low maturation rate of GFP allows the protein to aggregate inside the cell. Enhanced GFP (EGFP) is a derivative of the wild-type GFP with the 37 °C folding efficiency (F64L) point mutant to the scaffold produced by the single point mutation (S65T) with the improved spectral characteristics including increased fluorescence, photostability, and a shift of the major excitation peak to 488 nm, with the peak emission kept at 509 nm.

What is YFP

YFP (yellow fluorescent protein) is a GFP derivative introduced as a genetic mutation. Actually, it is a color mutant accomplished by the T203Y mutation. This results in π-electron stacking interactions between the substituted tyrosine residue and the chromophore. Therefore, YFP absorbs green color light at 514 nm wavelength while emitting yellow color light at 527 nm.

Figure 4: GFP Derivatives

Moreover, Citrine, Venus, and YPet are the three improved versions of YFP. They come with shared properties including reduced chloride sensitivity, faster maturation, and increased brightness. The main importance of YFP in molecular biology is to serve as the acceptor for genetically-encoded FRET (Förster resonance energy transfer) sensors. Here, the most common donor fluorescent protein is monomeric cyan fluorescent protein (mCFP), which another GFP derivative.

Similarities Between GFP and YFP

• GFP and YFP are two types of fluorescent proteins with similar applications in molecular biology.
• Both can emit fluorescence upon exposure to the light, which ranges from blue to the ultraviolet range.
• The genes of fluorescent proteins are used as reporters of gene expression.
• Also, these proteins can be expressed inside a variety of organisms including human, mammal, fish, fungal, yeast, and bacterial cells.
• Besides, the genes of fluorescent proteins are introduced into the host cells through recombinant DNA technology.

Difference Between GFP and YFP

Definition

GFP refers to a protein that glows green under fluorescent light and found naturally in the jellyfish, Aequorea Victoria, while YFP refers to a genetic mutant of green fluorescent protein (GFP). Thus, this is the fundamental difference between GFP and YFP.

Stands for

GFP stands for green fluorescent protein while YFP stands for yellow fluorescent protein.

Emitting Color under UV

As their names suggest, the main difference between GFP and YFP is that GFP emits green color light while YFP emits yellow color light.

Occurrence

Furthermore, GFP naturally occurs in many marine organisms including jellyfish, Aequorea Victoria while YFP is a genetic mutant of GFP. Hence, this is another difference between GFP and YFP.

Excitation Peak

Besides, the major excitation peak of GFP is at 395 nm and the minor excitation peak is at 475 nm while the excitation peak of YFP is at 514 nm.

Emission Peak

Also, the emission peak of GFP is at 509 nm while the emission peak of YFP is at 527 nm. Hence, this is also a difference between GFP and YFP.

Applications

Moreover, another important difference between GFP and YFP is that the GFP is important as a reporter of expression and to visualize the localization of the fused protein while YFP is used as non-invasive intracellular pH biosensors or fluorescent indicators for local Ca²⁺ concentrations.

Conclusion

GFP is a fluorescent protein that naturally occurs in the jellyfish, Aequorea Victoria. It used in molecular biology as a reporter of expression and to visualize the localization of the fused protein. Generally, GFP emits bright green fluorescence upon exposure to blue to ultraviolet light. In comparison, YFP is a genetic mutant of GFP, emitting yellow fluorescence upon the exposure to blue to ultraviolet light. Therefore, the main difference between GFP and YFP is the color of fluorescence they emit and their origin.

References:

1. “Green Fluorescent Protein (GFP).” Thermo Fisher Scientific, Thermo Fisher Scientific, Available Here.
2. Khetrapal, Afsaneh. “GFP Derivatives: CFP and YFP.” News-Medical.net, News Medical, 25 Jan. 2019, Available Here.

Image Courtesy:

1. “Aequorea victoria” By Mnolf – Photo taken in the Monterey Bay Aquarium, CA, USA (CC BY-SA 3.0) via Commons Wikimedia      
2. “PDB 1ema EBI” By Jawahar Swaminathan and MSD staff at the European Bioinformatics Institute (Public Domain) via Commons Wikimedia  
3. “Fgams ppat egfp puncta” By Zhao A, Tsechansky M, Swaminathan J, Cook L, Ellington AD, et al. (2013) Transiently Transfected Purine Biosynthetic Enzymes Form Stress Bodies. PLoS ONE 8(2): e56203. doi:10.1371/journal.pone.0056203 – http://www.plosone.org/article/info:doi/10.1371/journal.pone.0056203 (CC BY 3.0) via Commons Wikimedia     
4. “174-GFPLikeProteins GFP-like Proteins” By David Goodsell – RCSB Protein Data Bank Molecule of the Month (CC BY 3.0) via Commons Wikimedia