The structure of the putative Se-Met holliday junction DNA helicase (ruvB) from Campylobacter jejuni subsp. jejuni NCTC 11168 in complex with ADP was solved by SAD. There are two copies of the protein in the H32 space group’s asymmetric unit, which form a dimer with the buried surface area of ~2700 A2. Single chain of the putative helicase consists of three distinct domains and binds one copy of ADP molecule. All three domains are involved in dimerization. Examining the crystal packing, it can be seen that protein forms a hexamer with the buried surface area of 16460 A2 and having ~22 A wide channel in the middle of the oligomer.