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The Polymer Physics of Disordered Proteins

Seminar Group: 


Professor Ajay Gopinathan


Department of Physics
University of California, Merced


Friday, May 15, 2015 - 4:00pm


ESB 1001


Professor Cyrus Safinya

Intrinsically disordered proteins (IDPs), which form over a third of human proteins, challenge the structure-function paradigm because they function without ever folding into a unique three-dimensional structure. This presents an interesting opportunity to use the tools of polymer physics to gain insight into IDP dynamics and function. I shall present some of our recent efforts in this regard. One particularly fascinating example of IDP function is the nuclear pore complex (NPC) which gates nanoscale pores in the nuclear envelope and controls all nucleo-cytoplasmic traffic using a barrier composed of a large number of IDPs that fill the pore. Despite numerous studies, the actual structure of the barrier and its mechanism of operation are poorly understood primarily because of the disordered nature of these proteins. Here I will present our “bottom-up” approach using sequence analysis, course-grained simulations and polymer brush theory. Our results indicate that a particular, conserved arrangement of blocks at the individual protein level is critical to the formation of a unique, dynamic and switchable higher-order polymer brush architecture pointing to a novel form of gated transport in operation within the nuclear pore complex. Insights into this system can potentially be applied to the design of bio-mimetic filters that can achieve highly regulated transport across biological or in vitro membranes. The translocation across the cell wall of certain bacterial IDPs is another subject of interest. We show that the translocation depends only on cell geometry and protein length indicating that bacteria can exploit purely physical entropic mechanisms to perform this function.