Hi, I'm now facing a problem about selenomethionine-labelled protein crystallization.. Native protein crystallized very well and diffracted to 2.5A. However, SeMet-protein expression level decreased to only 1/10, and its crystals have different shape with before(native protein crystals have beautiful rhombohedral shape, while SeMet-protein crystals have a shuttle shape). For another crystalllization condition the SeMet protein don't crystallize at all while the native protein got crystals with even higher resolution. I don't know whether these "shuttle shaped" crystals are worthy to be used or not? But there are only 13 Met in my protein (43KD), why they have so much difference? Is this common, I mean, the huge difference between SeMet and native protein crystallization? And, any suggestions about what I can try to solve this Se-Met problem? (What I'm doing now is to screen crystallization kit with SeMet protein.)
Thank you very much for your help! best, Sarah
