Patent ID: 6906176

Claim:
A non-naturally occurring enterokinase-cleavable fusion protein comprising a polypeptide comprising the formula: Z 1 -Xaa 1 -Xaa 2 -Xaa 3 -Xaa 4 -Asp-Arg-Xaa 5 -Z 2 (SEQ ID NO:1), (1) wherein (a) Z 1 is a ligand recognition sequence; (b) Xaa 1 -Xaa 2 -Xaa 3 -Xaa 4 -Asp-Arg is an enterokinase recognition sequence, in which Xaa 1 is Ala, Asp, Glu, Phe, Gly, Ile, Asn, Ser, or Val; Xaa 2 is Ala, Asp, Glu, His, Ile, Leu, Met, Gln or Ser; Xaa 3 is Asp, Glu, Phe, His, Ile, Met, Asn, Pro, Val, or Tp; and Xaa 4 is Ala, Asp, Glu, or Thr; and (c) Xaa 5 -Z 2 is a protein of interest, in which Xaa 5 can be any amino acid and Z 2 is a polypeptide of at least one amino acid.