The giant elastic protein titin has many intrinsically disordered domains. Reversible stretching of the longest disordered PEVK segment generates resting tension, varying with isoform, phosphorylation and ligand/protein binding. To investigate the interplay between elasticity and protein interactions, we engineered a recombinant polyprotein with 15 identical SH3-binding PEVK modules.  Circular dichroism showed both its disorder and the presence of polyproline II helices. Atomic force data indicated a persistence length of 0.3 nm and a contour length of 176 nm.  ELISA data indicated its binding to nebulin SH3 at Kd 7 �M (4 �C) and 23 �M (25 �C). The binding of surface plasmon resonance are different from ELISA binding data, which may be a manifestation of shear-sensitivity of PEVK interactions. Interestingly, this binding appears shear-rate dependent in preliminary experiments and suggest the possibility that mechanical force may enhance SH3 binding upon stretching of PEVK.

Elastic scaffolding protein engineered from a SH3 binding Titin PEVK module

242nd National Meeting (2011)

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