Purification, crystallization and preliminary crystallographic analysis of Chlamydophila pneumoniae AP endonuclease IV

Base excision is a crucial DNA repair process mediated by endonuclease IV in nucleotide excision. In Chlamydia pneumoniae , Cp endoIV is the exclusive AP endonuclease IV, exhibiting DNA replication error-proofreading capabilities, making it a promising target for anti-chlamydial drug development. Predicting the structure of Cp endoIV, molecular docking with DNA was performed, analyzing complex binding sites and protein surface electrostatic potential. Comparative structural studies were conducted with E. coli EndoIV and DNA complex containing AP sites. Cp endoIV was cloned, expressed in E. coli , and purified via Ni-NTA chelation and sizeexclusion chromatography. Low NaCl concentrations induced aggregation during purification, while high concentrations enhanced purity. Cp endoIV recognizes and cleaving AP sites on dsDNA, and Zn 2 + influences the activity. Crystallization was achieved under 8% (v/v) Tacsimate pH 5.2, 25% (w/v) polyethylene glycol 3350, and 1.91 & Aring; resolution X-ray diffraction data was obtained at 100 K. This research is significant for provides a deeper understanding of Cp endoIV involvement in the base excision repair process, offering insights into Chlamydia pneumoniae .