I think it is very unlikely codon optimisation will improve solubility, so I'd save my money and use it to try other things. Assuming you have tried (much) lower temperatures for expression you could consider dialing down expression via a different promoter or low-copy number plasmid. I assume your protein is eukaryotic given you have tried insect cells. What about yeasts? I also assume your protein is not a membrane protein?
It's also good to keep in mind that funstional expression of such large protein is challenging to say the least. Bert ________________________________ From: CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> on behalf of Sutapa Chakrabarti <chakr...@zedat.fu-berlin.de> Sent: 03 April 2017 07:49 To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Using a codon-optimised gene to improve protein solubility Dear All, We’re trying to express and purify a 1000 residue long protein and have run into the problem that it is completely insoluble when expressed in E.coli and is not expressed at all in insect cells. The usual tricks for improving solubility in E.coli, such as addition of GST/MBP tags, optimising expression media and induction conditions and use of different cell strains, have not led to any improvement. We are now looking into ordering a codon-optimised synthetic gene for this protein and are trying to decide whether it would be worthwhile to codon-optimise for expression in E.coli (given that the protein was expressed but not soluble) or if we should attempt baculovirus expression again with a gene that has been codon-optimised for insect cells. My question is: has anyone observed an improvement in the solubility of their target protein using a codon optimised gene? I know of several instances where the use of a codon-optimised gene has led to expression where the native gene sequence did not but am unable to find any references for improvement in solubility. Since codon optimisation significantly alters the translation rate of a gene, I believe this should affect solubility as well; but I’d like to know what the community thinks/has observed before I order an exorbitantly priced gene! Thank you in advance, Sutapa -- Sutapa Chakrabarti, Ph.D. Institute of Chemistry and Biochemistry Freie Universität Berlin Takustr. 6 14195 Berlin Germany Phone: +49-(0)30-83875094
