Establishing the stability and reversibility of protein pyrophosphorylation with synthetic peptides.

Protein pyrophosphorylation is emerging as a new post-translational modification, yet its role in cellular signaling remains poorly characterized. Important factors in determining the biological relevance of pyrophosphorylation include understanding the chemical and biochemical stability of the pyrophosphoryl group and elucidating the reversibility of modification in a cellular context. Towards this end, we prepared a series of synthetic pyrophosphopeptides, which were utilized to demonstrate that the modification is quite inert over a wide pH range but can be removed biochemically by alkaline phosphatases. Importantly, we observed enzyme-dependent removal of the pyrophosphate in mammalian and yeast cell lysates using the synthetic pyrophosphopeptides. The findings provide evidence for the reversibility of pyrophosphorylation and thereby highlight the potential impact of this modification on cellular signal transduction pathways.