Identification and characterization of a phospo-arginine phosphatase (PAP) has been published in CELL REPORTS. Nice example that also small protein structures can be extremely thrilling – this time showing how a single, innocent residue near the active site turns out to be key in determining substrate specificity among protein phosphatases. Apparently, we have a PAP/PAK (YwlE phosphatase/McsB kinase) couple controlling protein arginine phosphorylation in bacteria.