Advances in Protein Structure Prediction Highlight Unexpected Commonalities Between Gram-positive and Gram-negative Conjugative T4SSs.

Despite recent advances in our understanding of the structure and function of conjugative Type 4 Secretion Systems (T4SSs), there is still only very scarce data available for the ones from Gram-positive (G) bacteria. This is a problem, as conjugative T4SSs are main drivers for the spread of antibiotic resistance genes and virulence factors. Here, we aim to increase our understanding of G systems, by using bioinformatic approaches to identify proteins that are conserved in all conjugative T4SS machineries and reviewing the current knowledge available for these components. We then combine this information with the most recent advances in structure prediction technologies to propose a structural model for a G T4SS from the model system encoded on pCF10. By doing so, we show that conjugative G T4SSs likely have more in common with their Gram-negative counterparts than previously expected, and we highlight the potential of predicted structural models to serve as a starting point for experimental design.