I recently did a western blot of a secretory protein, the result shows that the size of this protein in cell lysate is smaller then it in culture supernatant. Is this normal? Do some people have related literature？
Hi Lanshu Li
Post-translational modifications, such as glycosylation, can account for a lot of size changes, especially in proteins that are secreted. Glycosylation is often used to mark a protein for secretion and large sugar moieties will change the molecular weight - the proteins I work with are modified in this way and the size changes from ~45 kDa to over 60 kDa.
Hope this helps.
I completely agree with Jack Hopkins . PTMs may be playing role in the size increase of your secretory protein.
Hi,
I experienced a similar issue while I was trying to harvest a protein from the cytoplasm, periplasm, and the extracellular secretion of the host microbe. if your protein of interest has a specific assay for quantification of its functionality, I would suggest you to perform the same for the 2 versions of the protein to asses a compromise in its activity following the size change. Additionally, it would be nice if you mention the difference in the size range, which has been observed. As Dr. Hopkins says, PTM could be attributed to the difference, majorly a case observed while using eukaryotes.
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