Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 111, Issue 42, Pages 15048-15053Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1410796111
Keywords
ultrasensitivity; intrinsically disordered proteins; biosensors; synthetic biology; ribozymes
Categories
Funding
- Materials Research Science and Engineering Centers Program of the National Science Foundation [NSF DMR 1121053]
- NIH Grant [EB007689]
- Institute for Collaborative Biotechnologies through Grant from the US Army Research Office [W911NF-09-0001]
- European Research Council (ERC) [336493]
- National Sciences and Engineering Research Council of Canada Grant [RGPIN-2014-06403]
- Office Of The Director
- Office Of Internatl Science &Engineering [0968399] Funding Source: National Science Foundation
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Control over the sensitivity with which biomolecular receptors respond to small changes in the concentration of their target ligand is critical for the proper function of many cellular processes. Such control could likewise be of utility in artificial biotechnologies, such as biosensors, genetic logic gates, and smart materials, in which highly responsive behavior is of value. In nature, the control of molecular responsiveness is often achieved using Hilltype cooperativity, a mechanism in which sequential binding events on a multivalent receptor are coupled such that the first enhances the affinity of the next, producing a steep, higher-order dependence on target concentration. Here, we use an intrinsic-disorder-based mechanism that can be implemented without requiring detailed structural knowledge to rationally introduce this potentially useful property into several normally noncooperative biomolecules. To do so, we fabricate a tandem repeat of the receptor that is destabilized (unfolded) via the introduction of a long, unstructured loop. The first binding event requires the energetically unfavorable closing of this loop, reducing its affinity relative to that of the second binding event, which, in contrast occurs at a preformed site. Using this approach, we have rationally introduced cooperativity into three unrelated DNA aptamers, achieving in the best of these a Hill coefficient experimentally indistinguishable from the theoretically expected maximum. The extent of cooperativity and thus the steepness of the binding transition are, moreover, well modeled as simple functions of the energetic cost of binding-induced folding, speaking to the quantitative nature of this design strategy.
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