ChromoBlog

Crystal structure of the anti-GFP VHH-Green Fluorescent Protein complex.
The GFP Nanobody is displayed blue and the GFP in green color.

UV crosslinking techniques are the method of choice for a comprehensive analysis of in-vivo-mRNA targets of an RNA-binding protein (RBP). In the recent publication of Olgeiser et al. (2019), the authors applied individual-nucleotide resolution UV crosslinking and immunoprecipitation (iCLIP) to study fungal mRNA transport. For this approach, they have used strains expressing GFP-tagged versions of the two RBPs Grp1 and Rrm4; an optimized protocol was developed to uncover that Grp1 and Rrm4 conjointly bind thousands of shared target messenger ribonucleoproteins (mRNPs) in the fungus U. maydis. The protein:RNA complexes were immunoprecipitated in a multiple detergent containing buffer using ChromoTek’s GFP-Trap Magnetic Agarose. This is a transcriptome‐wide view to an endosomal mRNA transport machinery.

Introduction

Fluorescent proteins (FPs) have been used as protein tags since the mid-1990s mainly for cell biology and fluorescence microscopy. These tags have not only revolutionized cell biology by enabling the imaging of almost any protein, they are also used in biochemical applications. An important example is the immunoprecipitation and affinity purification of FP-tagged proteins, which was enabled by the development of affinity resins with high yield, purity, and affinity such as ChromoTek’s Nano-Traps (https://www.chromotek.com/products/detail/product-detail/nano-traps/).

In this blog we provide a review of

• green fluorescent proteins
• red fluorescent proteins
• self-labelling proteins, that require the covalent coupling of a fluorescent molecule

Jellyfish Green Fluorescent Protein (GFP) and its derivatives are still the most frequently used fluorescent proteins in biomedical research. Recently, additional green fluorescent proteins have been discovered in higher animals such as crustaceans and lancelets. These FPs share a common fold, but diverge widely in their primary sequence. Thus, they require novel, dedicated antibody research tools. Here is an overview about EGFP (the most commonly used GFP derivative), TurboGFP and mNeonGreen.

Life science laboratories apply green fluorescent proteins (GFP) to study protein localization, interaction and dynamics in fluorescence microscopy. Immunoprecipitation (IP), mass spectrometry (MS), co-immunoprecipitation (Co-IP) and/or affinity purification investigate more aspects including posttranslational modifications (PTMs), DNA binding, and protein-protein interaction. Here, we compare two different antibody systems for immunoprecipitation of GFP-fusion proteins: GFP-Trap and anti-GFP IgG antibody

Recently a new bright monomeric yellow-green fluorescent protein has been published, which is called mNeonGreen. This protein has already been frequently used for mainly microscopic applications in both wide-field microscopy and super resolution microscopy. What is mNeonGreen all about?

Although traditional IgG antibodies are often used for immunoprecipitation and protein interaction analysis, GFP-binding protein (GBP, ChromoTek gt-250) and other ChromoTek V_HHs (https://www.chromotek.com/about-us/the-alpaca-antibody-advantage/) easily outcompete those under challenging conditions such as elevated temperatures, varying pH or high denaturant concentrations. In fact, GBP tightly binds GFP-fusion proteins even in 8 M urea at 51 °C, which sets a new limit in protein complex stability, virtually unrivalled by any other capture molecule protein tag pair.