Abstract
To support conjugation via Type 4 Secretion Systems, relaxases perform the initial processing of the substrate DNA. TraI from the well-studied conjugative plasmid pKM101 is one such relaxase, which has not yet been characterized. Here, we report the crystal structure of the trans-esterase domain of TraI in complex with its substrate oriT DNA, highlighting the conserved DNA binding mechanism. Additionally, we present an apo structure of the trans-esterase domain of TraI, which allows us to visualize the conformational changes involved in DNA binding. We also show a complete characterization of the DNA binding, nicking and religation of the trans-esterase domain, helicase domain and full-length TraI. Furthermore, TraI is shown to be a tetramer. These results reveal that the trans-esterase domain behaves in a similar way as its homologs TraI from the F plasmid and TrwC from R388, but the tetramerization of the full-length protein highlights a significant difference that affects the function of TraI.
Competing Interest Statement
The authors have declared no competing interest.
