Catching protein polyphosphorylation in the act.

Lysine polyphosphorylation (K-PPn) is a relatively new post-translational modification, the full targets and functional consequences of which are unknown. A critical problem in the study of endogenous K-PPn of proteins in the yeast model system is that its nonenzymatic nature and its susceptibility to polyphosphatases make it potentially susceptible to artifacts during extraction. A new study confirms that K-PPn modifications can be altered during sample handling, provides new insights into the mechanism of K-PPn, and develops a yeast model strain, devoid of both vacuolar polyP and polyphosphatases, that allows detection of authentic endogenous K-PPn.