Bacillus anthracis pathogenicity is dependent upon on a number of virulence factors. Within these, protective antigen has a key role of delivering bacterial toxins into host cells. In order to carry out this function the protein must bind to host cell surface receptors and undergo proteolytic cleavage, multimerisation and refolding. This work demonstrates that the structural information driving this refolding is encoded within the full-length monomer, which is capable of undergoing the same transition. The N-terminal PA20 domain that is cleaved from the protein at the cell surface has the ability to bind to glycosaminoglycans; it may have a role outside the present model of intoxication as well as a role in initial folding the complete protein. As recombinant protective antigen is the immunogenic component of an experimental anthrax vaccine, its secondary structure and stability on the surface of the adjuvant Alhydrogel were studied. These were found to be close to those in solution, increasing the probability that the vaccine will raise protective antibodies.