An amino acid sequence is described. The amino acid may comprise a signal sequence that is SEQ ID NO. 1a (or a variant or homologue or derivative or fragment thereof) that is expressed as a fusion protein that comprises a protein of interest. The signal sequence directs secretion of the protein of interest. The protein of interest may be a heterologous protein. Secretion of the fusion protein aids purification.
1. A non-naturally occurring polypeptide comprising an amino acid sequence including a signal sequence consisting of SEQ ID NO: 6; wherein said polypeptide is not SEQ ID NO: 1.
2. The polypeptide of claim 1 wherein the amino acid sequence includes a protein of interest (POI).
3. The polypeptide of claim 2 wherein the signal sequence is either directly fused or indirectly fused to the N terminal end of the POI.
4. The polypeptide of claim 1 having the signal sequence at its N terminal end.
5. The polypeptide according to claim 4 wherein the signal sequence is directly fused or indirectly fused to a protein of interest (POI).
6. The polypeptide according to claim 5 wherein the signal sequence is directly fused or indirectly fused to the N terminal end of the POI.