ABSTRACT
GFP fusion-based fluorescence-detection size-exclusion chromatography (FSEC) has been widely employed for membrane protein expression screening. However, fused GFP itself may occasionally affect the expression and/or stability of the targeted membrane protein, leading to both false-positive and false-negative results in expression screening. Furthermore, GFP fusion technology is not well suited for some membrane proteins, depending on their membrane topology. Here, we developed an FSEC assay utilizing nanobody (Nb) technology, named FSEC-Nb, in which targeted membrane proteins are fused to a small peptide tag and recombinantly expressed. The whole-cell extracts are solubilized, mixed with anti-peptide Nb fused to GFP for FSEC analysis. FSEC-Nb enables the evaluation of the expression, monodispersity and thermostability of membrane proteins without the need for purification but does not require direct GFP fusion to targeted proteins. Our results show FSEC-Nb as a powerful tool for expression screening of membrane proteins for structural and functional studies.
Subject(s)
Chromatography, Gel , Green Fluorescent Proteins/metabolism , Membrane Proteins/metabolism , Nanotechnology , Peptides/metabolism , Single-Domain Antibodies/immunology , Animals , Cryoelectron Microscopy , Cysteine Loop Ligand-Gated Ion Channel Receptors/genetics , Cysteine Loop Ligand-Gated Ion Channel Receptors/immunology , Cysteine Loop Ligand-Gated Ion Channel Receptors/metabolism , Fish Proteins/genetics , Fish Proteins/immunology , Fish Proteins/metabolism , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/immunology , HEK293 Cells , Humans , Membrane Proteins/genetics , Membrane Proteins/immunology , Oryzias/genetics , Oryzias/metabolism , Peptides/genetics , Peptides/immunology , Protein Stability , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , Recombinant Fusion Proteins/metabolism , SARS-CoV-2/genetics , SARS-CoV-2/immunology , SARS-CoV-2/metabolism , Spectrometry, Fluorescence , Temperature , Viral Proteins/genetics , Viral Proteins/immunology , Viral Proteins/metabolismABSTRACT
Monoclonal antibodies are extremely valuable functional biomaterials that are widely used not only in life science research but also in antibody drugs and test drugs. There is also a strong need to develop high-quality neutralizing antibodies as soon as possible in order to stop the rapid spread of new infectious diseases such as the SARS-CoV-2 virus. This study has developed a membrane-type immunoglobulin-directed hybridoma screening (MIHS) method for obtaining high-quality monoclonal antibodies with high efficiency and high speed. In addition to these advantages, this paper demonstrates that the MIHS method can selectively obtain monoclonal antibodies that specifically recognize the functional structure of proteins. The MIHS method is a useful technology that greatly contributes to the research community because it can be easily introduced in any laboratory that uses a flow cytometer.