Factor Xa will work depending on the exact sequence. If your sequence starts MRS... and the start methionine is important and not removed then yes it will work when you clone it into a Factor Xa site. If however the start sequence starts RS... and the start methionine is actually removed, when you clone the gene minus the start Met, Factor Xa will not cleave IEGR/RS. Have you done Mass spec on the protein to confirm that the start methionine is removed/present?
Dan Dear Jerry, Whats about an N-terminal His-Tag with an Xa factor cleavage site behind it... After IMAC you only get protein with the entire N-Terminus (His-Tag), afterward digest the protein with Xa factor...it won’t leave any additional amino acids C-terminally! You’ll get your protein! ;) Cheers, Christian
