Biochemical and structural bioinformatics studies of fungal CutA nucleotidyltransferases explain their unusual specificity toward CTP and increased tendency for cytidine incorporation at the 3′-terminal positions of synthesized tails

Comparison of the 3D model of TtCutA with CTP, and available crystal structures of poly(U) polymerase Cid1 with UTP (pdb|4fh5), Cid1 (H336N) mutant with ATP (pdb|4fhx), and noncanonical poly(A) polymerase Trf4 (pdb|3nyb). Key amino acids forming a nucleobase binding pocket are shown in blue. Nucleotides are shown in magenta. Position of CTP in TtCutA was taken from pdb|4fhv. Selected water molecules responsible for interactions between Cid1 and UTP are denoted by red spheres.