Give me your advice, please - Is there a way to get a several milligrams of Rhodopsin with possibility of mutagenesis? If you know researchers who may know this, give me a message or link them!
I would suggest looking at the papers for the groups that solved the x-ray crystal structure to see what methods they used to obtain large amounts of protein.
I also pay in attention works of DeGrip, there are more modern protocols from this group. He really have good protocols, and now I search groups in Russia, or other countries who want collaborate with Russians researchers, and who can do works under DeGrip protocols.