The invention relates generally to an isolated peptide consisting of the amino acid sequence X1CX2WKX3CT, wherein X1 is F or A, X2 is F or Y and X3 is T or V in any combination or permutation, and wherein each of the amino acids is in the L- configuration and the peptide contains a disulphide bond between the two cysteine residues. Alternatively, the two sulphur atoms of the two cysteine residues may be linked via three carbon atoms. The invention also relates generally to fusion proteins comprising the peptide, to polynucleotides encoding the peptide or fusion proteins, to methods of producing the peptide or fusion proteins, to pharmaceuticals containing the peptide or fusion proteins, and to uses of the same.
