Structural investigation of Jun-Fos coiled coil interactions using NMR

Coiled-coils are the simplest example of a structure made from two separate protein chains. They are involved in a wide range of interactions both inside and outside the cell. Our studies, in collaboration with Dr. Jody Mason from the University of Essex, focus on the Jun-Fos system, which contains a repetitive and yet highly specific coiled coil motif that is responsible for mediating dimerisation. The Jun-Fos system forms the heterodimeric transcription factor Activator Protein-1 (AP-1), and it is known that particular homologues are deregulated or overexpressed in tumorigenic phenotypes. AP-1 represents a legitimate therapeutic target since it is found at the end of several cell signalling cascades (1). To probe how specific protein-protein interactions are achieved, we are employing a semi-rational library design approach in combination with a ‘Protein-fragment Complementation Assay’ to identify peptides that bind with high affinity for cFos or cJun (2, 3). While we now have a reasonable understanding of how these antagonists achieve stable interaction with their target (4, 5), nuclear magnetic resonance (NMR) spectroscopy studies will lead to high-resolution structures and understanding of dynamics in the coiled-coil, accelerating our research goal of understanding the molecular basis of stability and specificity at the atomic level. This project aims to express in bacteria and purify peptides for structural studies, obtain NMR spectra of different variants of the Jun-Fos coiled coil, and determine the structure of these semi-rationally designed peptide pairs. Understanding how one protein recognizes and binds another with high specificity is important not only for mapping protein networks, but also in devising peptide and peptidomimetic antagonists that can mimic natural proteins. The ultimate aim is to sequester one half of AP-1 as a non-functional heterodimer using an orally available peptidomimetic. Achieving this goal will first require understanding the molecular mechanisms of specific protein-protein interactions.

Applications are processed as soon as they are received, so early application is encouraged. NB applicants who wish to start their studies in October 2012 should submit their application by 31 July 2012. Applications received after this date will be considered for the January 2013 entry point if the project is still available.