The bacterial conjugation, the main route for horizontal gene transfer to prokaryotes, is a quick way for the evolution of bacterial genomes leading to organisms with new ecological or pathogenic characteristics. The acquisition of antibiotic resistance by pathogens is related to the conjugal transfer of mobile genetic elements. The transfer of genes between kingdoms, from bacteria to plants and fungi, are special cases of conjugation and even in cell division and sporulation, there are similar mechanisms for transfer.

The relaxase are DNA strand transferases that catalyze the initial and final stages of DNA processing during conjugal transfer, being, therefore, key enzymes in the process. Nuclease and ligase activities, helicases are also able to move along the DNA. Authors of the Institute of Molecular Biology, CSIC show that, in joining the origin of transfer, the relaxase TrwC distorts the DNA around the cutoff. Have resolved three-dimensional structure complexed with DNA relaxase, discovering that the protein is the point of attachment to DNA through recognition of the arms of a cruciform structure that forms in a reverse repeat, present in the origin of transfer sequence .

The structure is shown how the protein strongly embraces one of said arms, after which traps a single strand of DNA, which will be folded and introduced into the active site. The atomic structure of the relaxase, along with results obtained by site-directed mutagenesis experiments, to characterize in detail the architecture of the active site of this unique enzyme and analyze its enzymatic mechanism.