Hi, we are thinking about PEGylating a protein, for which dimerization or oligomerization seems to be important in its activity. Could this be affected by attaching PEG?
Thanks.
Yes, PEG is used to repel proteins from surfaces so the same will happen between pegylated protein molecules. Is it possible to run the pegylation when the protein is dimerized or oligomerized? If so then do it this way. If the protein is then subjected to monomerization, a posterior dimerization will be greatly affected.
Unless you can direct peggylation away from the oligomerization interface yes, it will be affected, either through direct linkage to residues involved in the interaction or by steric hindrance.
Yes. PEGylation will affect the oligomerization of your protein by sterically hindering the association or disrupting the interface. One way you could proceed is to try and direct the PEGylation far away from the binding interface and see if it works.
The percentage of bis-functionalized activated PEG in your reaction mixture is critical, since it can lead to covalently cross-linked dimers, tetramers and larger aggregates of the protein and, of course, to intramolecular cross-linking (loop-shaped PEG structures) within a single protein molecule.
On the other hand, attempting to put too many strands of PEG on the surface of an oligomeric protein can lead to disruption of the oligomeric structure. Thus if you're coupling PEG to the epsilon amino groups of lysine residues and there are only 5 such residues accessible on the surface of the protein, attempting to couple more than 5 PEGs could disrupt the structure and, in the case on an enzyme, could inactivate it, if the catalytic site involves more than one subunit.
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