Abstract: Streptokinase, a bacterial protein produced by various strains of haemolytic streptococci, is widely used to treat humans with thrombolytic disease. This protein is antigenic and anti- streptokinase antibodies (Abs) cause allergic reactions and neutralize streptokinase therapeutic effects. To produce an engineered variant of streptokinase being functional and less antigenic than the native molecule. In this study the C-terminal immunodoinant epitope of native molecule was eliminated by Polymerase Chain Reaction (PCR) using specific internal primers. Then PCR-amplified sequence was cloned into pGEMEX-1 expression vector.