A Fluorescent Probe for Protein Histidine Phosphatase Activity

Abstract

Protein histidine phosphorylation plays an important role in cell signaling and metabolic processes, particularly in bacteria, fungi, and plans. In mammals, protein histidine phosphatase (PHPT1) is one of a few characterized protein phosphatases specific towards phosphohistidine (pHis), and it is shown to regulate the activities of diverse ion channels as well as metabolic proteins. Its activity has been linked to cancer metastasis and diabetes, but further studies have been hampered due to the lack of suitable tools including convenient and accurate phosphatase activity assays. Previous assays relying on a radiolabeling are hazardous and technically laborious. While chromogenic or fluorogenic small molecule substrates have also been used, they are nonselective towards PHPT1 and their kinetic parameters are different from native substrates. To address this, we herein report a fluorescent probe for the pHis activity of PHPT1. With this probe, we conveniently obtained the kinetic parameters of PHPT1 towards a pHis substrate, which showed orders of magnitude difference from the literature values. Our probe was also selective towards PHPT1 over a panel of phosphatases, potentially applicable in monitoring PHPT1 activities in biological samples.