Oedema factor (EF) — a calmodulin-activated adenylyl cyclase — is important in the pathogenesis of anthrax, but the relationship between the structure of EF and its function remains unclear. In January 24
Drum et al. examined the X-ray structures of EF and found that four discrete regions form a surface that recognizes an extended conformation of calmodulin. On calmodulin binding, an EF helical domain of relative molecular mass 15,000 undergoes a 15 Å translation and a 30º rotation away from the EF catalytic core, which stabilizes a disordered loop and leads to enzyme activation (Nature 2002, 415:396-402). The calmodulin is subsequently unable to effectively regulate cellular cyclic AMP levels, with the result that the cell can no longer regulate its water content — hence the oedema. ...
