seq id no 3 in that one or more amino acid residues are inserted deleted or replaced with other different amino acid residues preferably the amino acid changes are of minor nature i e conservative amino acid substitutions which will not influence the folding and or activity of the protein significantly small deletions usually of 1 to about 30 amino acids in length small extensions at amino or carboxyl terminus e g the methionine residue at amino terminal small connective peptide up to about 20 25 residues in length or small extensions that will facilitate purification by changing the net charge or that have other functions e g poly histidine tract antigenic epitopes or binding domains the present inventor discovered that the thrombolytic and anticoagulant functions of the expression products remained almost unchanged when the coding sequence of the 6 10 amino acids nh 2 terminal of rgd sak or kgd sak was removed by deletion mutation the thrombolytic activity of the expressions was lost when the coding sequence of the 10 15 nh 2 terminal amino acids was removed and the above bifunctionality of the expression products remained almost unchanged when the coding sequence of the 15 nh 2 terminal amino acids was removed and the ser at position 16 was changed to lys wild type r sak prepared by our laboratory 970923 was more than 98 pure and stored at u2212 70 u00b0 c reductive and non reductive sds page performed according to the method of laemmli see molecular cloning a laboratory manual loading buffer containing 0 0625 mol l tris hcl ph6 7 2 sds 10 glycerol 5 mercaptoethanol and 0 001 bromophenol blue sample.