Multi-copy genes that enhance the yield of mammalian G protein-coupled receptors in Escherichia coli


Low yields of recombinant expression represent a major barrier to the physical characterization of membrane proteins. Here, we have identified genes that globally enhance the production of properly folded G protein-coupled receptors (GPCRs) in Escherichia coli. Libraries of bacterial chromosomal fragments were screened using two separate systems that monitor: (i) elevated fluorescence conferred by enhanced expression of GPCR–GFP fusions and (ii) increased binding of fluorescent ligand in cells producing more active receptor. Three multi-copy hits were isolated by both methods: nagD, encoding the ribonucleotide phosphatase NagD; a fragment of nlpD, encoding a truncation of the predicted lipoprotein NlpD, and the three-gene cluster ptsN–yhbJ–npr, encoding three proteins of the nitrogen phosphotransferase system. Expression of these genes resulted in a 3- to 10-fold increase in the yields of different mammalian GPCRs. Our data is consistent with the hypothesis that the expression of these genes may serve to maintain the integrity of the bacterial periplasm and to provide a favorable environment for proper membrane protein folding, possibly by inducing a fine-tuned stress response and/or via modifying the composition of the bacterial cell envelope.




Copyright 2012 Metabolic Engineering. This is a post-print version of a published paper that is available at: Recommended citation:Skretas, Georgios, Tomohiro Makino, Navin Varadarajan, Mark Pogson, and George Georgiou. "Multi-copy genes that enhance the yield of mammalian G protein-coupled receptors in Escherichia coli." Metabolic engineering 14, no. 5 (2012): 591-602. doi: 10.1016/j.ymben.2012.05.001. This item has been deposited in accordance with the publisher copyright and licensing terms and with the author's permission.