I purified one recombinant protein, in polyacrylamide gel the expected weight is 45kDa but the band of this protein is 55kDa aproximately.
Proteins do not always run at precisely the position in SDS-PAGE that would be expected based on the mass of the protein. This can be because of post-translational modifications, insufficient reduction of disulfide bonds, resistance of part of the protein to denaturation, or an unusual amino acid composition.
Dear Laura Lorena Garcia
You think as a scientist, you can have the answer in your mind and hand for your question what you have raised here.
All the best.
Proteins do not always run at precisely the position in SDS-PAGE that would be expected based on the mass of the protein. This can be because of post-translational modifications, insufficient reduction of disulfide bonds, resistance of part of the protein to denaturation, or an unusual amino acid composition.
The unexpected (higher than expected) SDS-PAGE mobility is ususally the result of post-translational modifications (if you work in eukaryotic system) and/or rather high or low isoelectric point.
In practice, we usually ignore the theoretical/observed Mw difference less or equal to 5 kDa, otherwise we use MS/MS to confirm the identity of the protein and to identify any possible PTMs.
Amaj that could be due to incomplete reduction by your reducing agent or some post translational modifications.
Do you have any tag? perhaps you have not consider yet a His-Tag and that is the reason why you see the band in a different weight.
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