BSE is believed to be caused by a specific protein which becomes altered or ‘misfolded’. This protein is called a prion. It is this prion protein which can carry the disease from individual to individual, and which causes the deterioration of the brain and spinal cord. Under normal circumstances the prion protein is arranged in an alpha helical arrangement (resembling a spring). However, some animals carry a particular allele, which makes this previously normal protein contort into a different arrangement of molecules, called a beta pleated sheet. It is this malfunction of the protein which is the disease-causing shape, and which is often referred to as the ‘infectious agent’ of BSE.
