Bringing Histidine Phosphorylation into Light: Role of Chemical Tools

Histidine phosphorylation is a historically underexplored post-translational modification (PTM). Once deemed "elusive" due to its chemical lability, phosphohistidine (pHis) has recently come to light thanks to emerging chemical tools-including stable pHis analogs, pHis-specific antibodies, and tailored proteomics workflows-that enable its detection and functional analysis. Together, these innovations have led to a surge in the identification of pHis sites and raised awareness of their roles in both bacterial and mammalian systems. New assay systems have also facilitated the characterization of histidine kinases and phosphatases. This Review summarizes recent breakthroughs in pHis research tools, examines the limitations of current approaches, and outlines future tools needed to fully unravel the potential of histidine phosphorylation.