Proteins tend not to work in isolation but interact with other proteins either in stable complexes or transiently, e.g. proteases that cleave their target proteins. Moreover how these proteins interact often relies on a conformational change, large or small. Membrane attack complex/perforin-like (MACPF) proteins are an excellent example of self-assembly integral membrane proteins and comprise the largest superfamily of pore forming proteins. These pore forming proteins play crucial roles in immunity, venom toxicity, fungal defense, pathogenesis and uncharacterized roles in development biology. Moreover the MACPF family share a common evolutionary ancestor with the CDC family of pore forming toxins from Gram positive bacteria. The over-arching mechanism of this MACPF/CDC superfamily starts with soluble monomeric proteins that recognise and assemble on the target membrane into a large ring-shaped oligomer. The oligomer can then undergo a massive conformational change to become an integral membrane protein complex. These membrane complexes range from 1–3 Mega Daltons in size and are capable of the passive transport of folded globular proteins. Recently, the field has started to tackle the outstanding questions of the MACPF field by combining single particle cryo-electron microscopy (SP cryo-EM), also named “Method of the Year 2015” by Nature Methods, with cutting edge computational and biophysics techniques. In principle, these combined methods can equally be applied to study other protein complex formation and conformational change. This presnetation will show the results of a combined phylogenetic and structural biology study of the MACPF/CDC family: Firstly, the cholesterol dependent cytolysins from Gram positive bacteria . Secondly, pleurotolysin, a toxin from a carnivorous mushroom . And finally the immune proteins, MAC and perforin . The most up-to-date structural and biophysical knowledge of these three clades helps us understand how the common mechanism of MACPF/CDC proteins evolved. More importantly, by studying a diverse set of MACPF/CDC proteins we see how the common MACPF/CDC fold has evolved for specific activities within the organism and the role of the ancillary domains in modulating the MACPF/CDC fold activity.