This post was contributed by guest blogger Natalie Niemi, a postdoctoral fellow at the Morgridge Institute for Research in Madison, Wisconsin.
It is commonly cited that approximately one-third of cellular proteins are modified through phosphorylation (1). However, the expansion of studies on protein phosphorylation in an array of model systems coupled with advances in mass spectrometry suggest that phosphorylation is far more prevalent than previously appreciated. PhosphoSitePlus, one of the most inclusive databases of post-translational modifications, identifies a staggering ~250,000 phosphorylation events in the proteomes of higher mammals (2). How can we begin to understand the importance of any of these phosphorylation events on the activity of a given protein?