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bioRxiv · 10.1101/063776

Biophysical assay for tethered signaling reactions reveals tether-controlled activity for the phosphatase SHP-1

Jesse Goyette·Citlali Solis Salas·Nicola Coker Gordon·Marcus Bridge·Samuel I Isaacson·Jun Allard·Omer Dushek
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Abstract

Tethered enzymatic reactions are ubiquitous in signalling networks but are poorly understood. Here, a novel mathematical analysis is established for tethered signalling reactions in surface plasmon resonance (SPR). Applying the method to the phosphatase SHP-1 interacting with a phosphorylated tether corresponding to an immune receptor cytoplasmic tail provides 5 biophysical/biochemical constants from a single SPR experiment: two binding rates, two catalytic rates, and a reach parameter. Tether binding increased the activity of SHP-1 by 900-fold through a binding-induced allosteric activation (20-fold) and a more significant increase in local sub-strate concentration (45-fold). The reach parameter indicates that this local substrate concentration is exquisitely sensitive to receptor clustering. We further show that truncation of the tether leads not only to a lower reach but also to lower binding and catalysis. The work establishes a new framework for studying tethered signalling processes and highlights the tether as a control parameter in clustered signalling.

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Jesse Goyette, Citlali Solis Salas, Nicola Coker Gordon, Marcus Bridge, Samuel I Isaacson, Jun Allard, Omer Dushek. 2016-07-14. Biophysical assay for tethered signaling reactions reveals tether-controlled activity for the phosphatase SHP-1. https://doi.org/10.1101/063776

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