Structure? Who needs structure?

One of the more interesting aspects of the polyadenylation complex is the nature of the protein-protein interactions that help shape the machinery. A recent study has revealed a fascinating side of this story. It involves the interaction between a subunit known as Fip1 (Fip = Factor Interacting with Poly(A) polymerase) and poly(A) polymerase (affectionately abbreviated as PAP). This study is remarkable for two reasons. For one, it dispels some previously-held notions about the functional significance of this interaction. In addition, it reveals that Fip1 is a member of a large class of proteins that share a common feature – namely, they do not have a rigidly-specified 3-dimensional structure in and of themselves.