The C-terminus of polymerase A in E coli is arginine-rich and is necessary for full functioning of the enzyme.

1: Poly(A) polymerase I of Escherichia coli: characterization of the catalytic domain, an RNA binding site and regions for the interaction with proteins involved in mRNA degradation. Raynal LC, Carpousis AJ; Mol Microbiol. 1999;32:765-775. PMID:10361280