Phosphorylation of Escherichia Coli Poly(A) Polymerase I and Effects of This Modification on the Enzyme Activity

In Escherichia coli, RNA polyadenylation is catalyzed mainly by poly(A) polymerase I (PAP I). Here we demonstrate that a PAP I variant with a C-terminal His tag (PAP I-His) can be phosphorylated both in vivo and in an artificial in vitro system. The in vivo phosphorylation of PAP I-His impairs activity of this enzyme. Previous studies, performed by others, indicated that phosphorylation of His-tagged proteins usually reflects such a modification of their native counterparts in bacterial cells. Therefore, our results suggest that phosphorylation and dephosphorylation of PAP I may be important regulatory processes in the control of activity of this enzyme.