A crystallization and preliminary X-ray diffraction study of the Arabidopsis thaliana proliferating cell nuclear antigen (PCNA2) alone and in a complex with a PIP-box peptide from Flap endonuclease 1

DNA replication is an important event for all living organisms and the mechanism is essentially conserved from archaea, bacteria to eukaryotes. Proliferating cell nuclear antigen (PCNA) acts as the universal platform for many DNA transacting proteins. Flap endonuclease 1 (FEN1) is one such enzyme whose activity is largely affected by the interaction with PCNA. To elucidate the key interactions between plant PCNA and FEN1 and possible structural change of PCNA caused by binding of FEN1 at the atomic level, crystallization and preliminary studies of X-ray diffraction of crystals of Arabidopsis thaliana PCNA2 (AtPCNA2) alone and in a complex with a peptide derived from AtFEN1, which contains a typical PCNA-interacting protein (PIP)-box motif, were performed. Both peptide-free and peptide-bound AtPCNA2s were crystallized using the same reservoir solution but in different crystal systems, indicating that the peptide affected the intermolecular interactions in the crystals. Crystals of AtPCNA2 belonged to the hexagonal space group P63, while those of the peptide-bound AtPCNA2 belonged to the rhombohedral space group H3, both of which could contain the functional homo-trimers.