CLP1_P is the P-loop carrying domain of Clp1 mRNA cleavage and polyadenylation factor, Clp1, proteins in eukaryotes. Clp1 is essential for 3'-end processing of mRNAs. This region carries the P-loop suggesting it is the region that binds adenine or guanine nucleotide [1].

1: Structure of a nucleotide-bound Clp1-Pcf11 polyadenylation factor. Noble CG, Beuth B, Taylor IA; Nucleic Acids Res. 2007;35:87-99. PMID:17151076