Zn(II)-mediated gold nanosensors for protein phosphatase assay

Abstract

Protein phosphatases (PPs) have served as key molecules in a myriad of biological events. Since gold nanoparticle (AuNP)-based colorimetric assays have been preferred for enzyme activity assay, a few of attempts have been designed for the simple and rapid detection of PP activity. Here we report a simple AuNP colorimetric assay of PP activity using hexahistidine-tagged phosphopeptides and divalent metal ions, which does not require antibody and rare chemical. Among metal ions including nickel (II), copper(II), cobalt(II), magnesium (II), manganese (II), and zinc(II), only zinc (II) triggered self-assembly of AuNPs in the presence of hexahistidine-tagged phosphopeptides. In contrast, PP1 caused dephosphorylation of peptides, leading to no change in the color of the AuNP solution. As a result, the PP activity was easily quantified by the extinction ratio (E520/E700) of the colloidal gold assembly, where there was a linear correlation between the PP concentration and the extinction ratio. Most importantly, this method was successfully used for analyzing protein phosphatase 2A (PP2A) activity in immunoprecipitated plant extracts. Based on the results, we anticipate that out method will find the applications to monitor the activities of various PPs and their inhibition in a rapid format. Copyright 2015 by TechConnect. All rights reserved.