Disordered Motifs and Domains in Cell Control - October 11-15, 2014

Disordered Motifs and Domains in Cell Control

Monday Speaker Abstracts

Intrinsically Disordered Titin PEVK Motifs: The Interplay of Force, Form, and Function of an Ion-exchange Driven Elastomer Kuan Wang 1,3 , Richard J. Wittebort 2 , Leffrey G. Forbes 3 , Wanxia L. Tsai 3 , S Arumugam 2 . 1 Academia Sinica, Nankang, Taipei, Taiwan, 2 University of Louisville, Louisville, KY, USA, 3 NIAMS, NIH, Bethesda, MD, USA. We describe the interplay between elasticity and ensemble structures of intrinsically disordered proteins, using the PEVK segment of the giant (~3-4 MDa) elastic protein titin as a model. Titin PEVK is an highly extended scaffold protein segment encoded by splicing of more than 100 exons and is thought to integrate mechanical stress and SH3-mediated signaling pathways (J. Biol. Chem,281, 27539-556, 2006). Solution and gel phase NMR, single molecule force spectroscopy and steered molecular dynamics simulations were used to investigate the ensemble structures and ion-pair interactions of an engineered 15-mer polyprotein, consisting of 15 identical titin PEVK modules, with affinity tags at both ends to facilitate nanomechanical measurements by single molecule atomic force microscopy. Using the NMR data for the polypeptide backbone and a subset of possible long range interactions, we were able to simulate an ensemble of representative structures and to simulate the mechanical stretching of a trimer and compare it to the stretching of the single polyprotein by atomic force microscopy. The stretching simulations showed that the attractive ionic interactions are in constant flux, leading to an elastic behavior similar to entropic polymers. Some of the simulations showed the exact force signature as those seen in experimental force spectra, and the force-bearing events arise from either transient hydrophobic residues, depending upon the trajectory of the stretching polymer. The current work tightly integrates both experiments and simulations to provide a more complete understanding of how intrinsically disordered ampholytes behaves as an elastic element by an intrachain ion-exchange mechanism. Our insights of nanomechanical properties of this intrinsically disordered protein are useful in the understanding of how force modulates function and in the design of elastic functional elastic biomaterials.

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