The present invention concerns a protein comprising a mutated sequence of SEQ ID No. 1, said mutated sequence of SEQ ID No. 1 comprising at least one mutation A, A′, B, C or C′, in which:mutation A consists of substituting amino acids 43 to 52 of sequence SEQ ID No. 1 with a sequence chosen from DFLAEGLTPR, KATN*ATLSPR and KATXATLSPR,mutation A′ consists of substituting amino acids 47 to 52 of sequence SEQ ID No. 1 with a sequence chosen from TSKLTR, FNDFTR, LSSMTR, PPSLTR and LSCGQR,mutation B consists of inserting a sequence chosen from DFLAEGLTPR, KATN*ATLSPR, KATXATLSPR, TSKLTR, FNDFTR, LSSMTR, PPSLTR and LSCGQR, between amino acids 52 and 53 of sequence SEQ ID No. 1,mutation C consists of inserting a sequence chosen from DFLAEGLTPR, KATN*ATLSPR and KATXATLSPR, between amino acids 52 and 53 of sequence SEQ ID No. 1, and of deleting amino acids 4 to 13 from sequence SEQ ID No. 1,mutation C′ consists of inserting a sequence chosen from TSKLTR, FNDFTR, LSSMTR, PPSLTR and LSCGQR, between amino acids 52 and 53 of sequence SEQ ID No. 1, and of deleting amino acids 4 to 9 from sequence SEQ ID No. 1.
