Using Haloarcula marismortui bacteriorhodopsin as a fusion tag for enhancing and visible expression of integral membrane proteins in Escherichia coli

• Published in: PloS one 2013-02, Vol.8 (2), p.e56363-e56363
• Main Authors: Hsu, Min-Feng, Yu, Tsung-Fu, Chou, Chia-Cheng, Fu, Hsu-Yuan, Yang, Chii-Shen, Wang, Andrew H J
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacteriorhodopsin; Bacteriorhodopsins - chemistry; Bacteriorhodopsins - genetics; Biological activity; Biology; Carnitine; Cytochrome; E coli; Escherichia coli; Escherichia coli - genetics; Eye; Gene Expression; Genetic Engineering - methods; Genomes; Haloarcula marismortui - genetics; Histidine; Integral membrane proteins; Integrals; Membrane proteins; Models, Molecular; Molecular Sequence Data; Organic Cation Transport Proteins - chemistry; Organic Cation Transport Proteins - genetics; Organic Cation Transport Proteins - isolation & purification; Organic Cation Transport Proteins - metabolism; Pharmacology; Phosphatase; Phosphatases; Phosphates; Physics; Proteases; Protein expression; Protein purification; Protein Structure, Secondary; Proteins; Proteolysis; Purification; Pyrophosphatases - chemistry; Pyrophosphatases - genetics; Pyrophosphatases - isolation & purification; Pyrophosphatases - metabolism; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - isolation & purification; Recombinant Fusion Proteins - metabolism; Rhodopsin; Structure-function relationships; Target detection; Undecaprenyl pyrophosphate
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0056363

Membrane proteins are key targets for pharmacological intervention because of their vital functions. Structural and functional studies of membrane proteins have been severely hampered because of the difficulties in producing sufficient quantities of properly folded and biologically active proteins. Here we generate a high-level expression system of integral membrane proteins in Escherichia coli by using a mutated bacteriorhodopsin (BR) from Haloarcula marismortui (HmBRI/D94N) as a fusion partner. A purification strategy was designed by incorporating a His-tag on the target membrane protein for affinity purification and an appropriate protease cleavage site to generate the final products. The fusion system can be used to detect the intended target membrane proteins during overexpression and purification either with the naked eye or by directly monitoring their characteristic optical absorption. In this study, we applied this approach to produce two functional integral membrane proteins, undecaprenyl pyrophosphate phosphatase and carnitine/butyrobetaine antiporter with significant yield enhancement. This technology could facilitate the development of a high-throughput strategy to screen for conditions that improve the yield of correctly folded target membrane proteins. Other robust BRs can also be incorporated in this system.