Nucleic acid molecules encoding transmembrane serine proteases, the encoded proteins and methods based thereon

A nucleic acid molecule, comprising a sequence of nucleic acids encoding a single chain polypeptide that consists only of a protease domain of a type-II membrane-type serine protease (MTSP), or a proteolytically active fragment thereof, as a single chain, wherein:

• a free Cys in the protease domain, which is normally disulfide bonded to a Cys in the pro-domain of the full length MTSP, is replaced with another amino acid;
• the nucleic acid molecule contains a stop codon so that only the single chain MTSP protease domain, or proteolytically active fragment thereof, can be expressed;
• and
• the MTSP protease domain, or proteolytically active fragment thereof, has serine protease activity as a single chain.