The leader sequence of streptokinase is responsible for its post-translational carboxyl-terminal cleavage

When the expression of streptokinase from two tac promoter-controlled expression vectors, one of these deleted a putative leader sequence of streptokinase and the other not, was compared, both normal and degraded streptokinase were detected in proteins expressed from the leader-contained vector, but only normal streptokinase was detected from the leader-deleted vector. These findings indicate that the characteristic carboxyl-terminal cleavage of streptokinase is correlated with its leader sequence and occurs during the defective secretion. The homogeneous preparation of streptokinase was facilitated by expressing from this leader-deleted vector.