Hi

First of all, in my experience protein markers are not 100% accurate.

Secondly, your protein might be getting processed during expression. If so, its only around 3-4 Kd thats being processed out and you cant see it.

Thanks

An observed mol. wt. of 20 kDa for a 23.6 kDa protein does not seem alarming to me.

Depending on the source of your molecular weight (e.g. protparam), I agree with Rahul Kumar that post-translational modifications (e.g. glycosylation) can alter it.

Additionnally, the migration in electrophoresis can be altered by charged residues on your protein.

If your protein has disulfide bonds, consider whether you want to run your gel under reducive conditions or not.

Hope this helps!

Sometimes proteins may appear differently compare to their predicted mass, origin of the protein could be the reason as if the protein is recombinant or natural. May be due the post transnational modification mass of desired protein changes and band appear at different position than actual mass. You can survey the literature of same protein blot and perform at similar conditions (same lysis buffer).  mix well the and care in gel preparation. hope this will be helpful

Thank you Rahul Kumar, Charles Fortier and Abdul Rehman for the answers.

Hi,

I agree with Rahul Kumar that the markers are not 100% accurate. However, this is also quite possible that the band you see is not full length protein but a degradation product. I would suggest you if possible to determine the full mass of the protein (from the protein band observed on SDS-PAGE) by mass spectrometry analysis, this will precisely tell you if your protein is full length or degraded.