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B、IPTG(-/+) = without/with 0.2 mM IPTG for 3-6 hours, adding IPTG to a bacteria culture with OD600 0.2-0.3. M: Protein molecular weight marker ladder. Lane 1～6: pET28 plasmids encoding crtI(BBa_K4162016)，BCMO(BBa_K4162022) without any tag were transformed into BL21(DE3) Rosetta strain, single clones (I3, BCMO1, BCMO2 ) were picked for liquid LB culture. Lane 8~17: pET28 plasmids encoding crtI(BBa_K4162016)，crtB(BBa_K4162013), crtE(BBa_K4162010)，crtY(BBa_K4162019) without any tag were transformed into BL21(DE3) HI-Control strain, single clones (I6, I7, B1, E1, Y1) were picked for liquid LB culture. Protein expression was induced in parallel cultures by IPTG. Bacterial cultures were monitored by OD600, and 5x10^7 cells were harvested by centrifugation and lysis in 1x SDS sample buffer. Equal amount (10 μL, 2x10^6 cells) of whole cell lysate were analyzed by SDS-PAGE (4~20% gradient gel, Tanon brand). Red arrows point to crtI protein. Green arrows point to crtY protein. Black arrows point to crtB protein. Yellow arrows point to crtE protein.