I purify a small GTPase from E.coli and it copurifies with a molecule of 609 or 610 Daltons. It's not GTP, does anyone have an idea about what it might be?
@Vladimir: The GpA/ApG sounds like a possibility, thanks!
@Kez: Affinity / Ion-exchange / Gel-filtration
Any idea about what it might be? CAS 27025-41-8
2-amino-4-[[2-[2-[(4-amino-4-carboxy-butanoyl)amino]-2-(carboxymethylcarbamoyl)ethyl]disulfanyl-1-(carboxymethylcarbamoyl)ethyl]carbamoyl]butanoic acid
To Victor: In other words this might be an oxidized form of glutathione (GSSG). It's possible (if it binds GTPase) as GSH is synthesized in E.coli (and then can be oxidized to GSSG). Interesting choice.
I meant. From the MW it should be a hexa-peptide. Could be a fragment of your GTPase.
I would try electrophoresis with Urea to see how "pure" is your preparation. Gradient of poly-acrylamide would be preferable. Then elute the band out of the gel and analyze the "polypeptide" separately, try MALDI-TOF.
Did you use detergent to purify your small GTPase? Some detergents sometime stick to these proteins. Could it also be some glycerides or other membrane constitutents?
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