Bright Makes This Green Light Right
Monster Green Protein: A Brighter, Longer-Expressing Green Fluorescent Protein
By Brian D. Almond, Ph.D., Promega Corporation
Abstract
Promega recently introduced the Monster Green Fluorescent Protein, a novel gfp gene cloned from Montastrea cavernosa. The Monster Green Fluorescent Protein reporter gene (hMGFP) has been "humanized" to increase expression and ensure reliability. Experimental results show that Monster Green Fluorescent Protein results in a brighter signal and expression that persists longer than other commercially available GFPs.
Translation of the MGFP gene involves codons not frequently used in mammalian cells, which can reduce MGFP expression efficiency in mammalian cells. To improve expression levels, the synthetic hMGFP gene uses only the highest usage mammalian codons. To further increase mammalian expression efficiency, the Kozak sequence for translation initiation has been added to the beginning of the gene. As well, other undesirable elements, including eukaryotic polyadenylation signals (AATAAA) have been removed.
Monster Green Fluorescent Protein is encoded by an improved synthetic version of the green fluorescent protein gene originally cloned from the great star coral Montastrea cavernosa. Introduction
Green fluorescent protein (GFP) is commonly used to monitor gene expression and intracellular protein trafficking. GFP fusion proteins, which are easily visualized by standard fluorescence microscopy, are used to track real-time subcellular localization of proteins of interest. Promega's Monster Green Fluorescent Protein is encoded by an improved synthetic version of the green fluorescent protein gene originally cloned from the great star coral Montastrea cavernosa. The native Montastrea gfp gene expresses a protein that photobleaches and produces a very faint fluorescent signal, making it unsuitable as a reporter. To improve the fluorescent properties of the native GFP, random mutagenesis was performed, resulting in the generation of a MGFP clone. The clone expresses a GFP that is resistant to photobleaching and is brighter than the native gene. The MGFP gene also contains many consensus transcription factor binding sites that can result in nonspecific transcriptional activation under certain experimental conditions. The numerous transcription factor binding sites compromise the reliability of MGFP as a reporter. To improve reliability of protein expression, the number of consensus transcription factor binding sites has been reduced from 67 in the MGFP gene to 3 in the synthetic hMGFP ("humanized" MGFP; Figure 1).

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