PROCESSING OF FUSION PROTEINS WITH IMMOBILIZED FACTOR XA

Factor Xa, with a cellulose-binding domain (CBD) fused to the C-termin us of the heavy chain (FXa-CBD), is active in solution and when immobi lized on cellulose. A second derivative of factor Xa in which a hexahi stidine tail is fused to the C-terminus of the. heavy chain (FXa-H-6) also retains activity when immobilized, in this case on Ni2+-NTA agaro se. The stabilities and activities of FXa-CBD and FXa-H-6 immobilized on cellulose and Ni2+-NTA agarose, respectively, are similar. Immobili zed factor Xa derivatives can be used to remove affinity tags from app ropriate fusion proteins without contaminating the desired product wit h factor Xa.