Chimeric systems composed of swapped Tra subunits between distantly-related F plasmids reveal striking plasticity among type IV secretion machines

• DOI: 10.1371/journal.pgen.1011088
• Publication Date: 2024-03-04T18:32:58Z
• Authors: Kouhei Kishida; Yang Grace Li; Natsumi Ogawa-Kis...; Pratick Khara; Abu Amar M. Al Mamun; Rachel E. Bosserman; Peter J. Christie
• Keywords: Bacterial conjugation; Heterologous

Bacterial type IV secretion systems (T4SSs) are a versatile family of macromolecular translocators, collectively able to recruit diverse DNA and protein substrates deliver them wide range cell types. Presently, there is little understanding how T4SSs recognize substrate repertoires form productive contacts with specific target cells. Although composed number conserved subunits adopt certain structural features, they also display considerable compositional diversity. Here, we explored the bases underlying functional versatility through systematic deletion subunit swapping between two conjugation encoded by distantly-related IncF plasmids, pED208 F. We identified several regions intrinsic flexibility among T4SSs, as evidenced partial or complete functionality chimeric machines. Swapping VirD4-like TraD coupling proteins (T4CPs) yielded chimeras, indicative relaxed specificity at substrate—TraD TraD—T4SS interfaces. Through mutational analyses, further delineated domains T4CPs contributing recruitment cognate vs heterologous substrates. Remarkably, swaps components comprising outer membrane core complexes, few F-specific subunits, TraA pilins supported transfer in absence detectable pilus production. Among sequenced enterobacterial species NCBI database, many strains that harbor more F-like plasmids F lacking one T4SS required for self-transfer. confirmed host cells carrying co-resident, non-selftransmissible variants elaborate transmission both plasmids. propose plasticity enables facile assembly this level can account diversification superfamily over evolutionary time and, on immediate time-scale, proliferation transfer-defective MGEs nature.