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Instruments / Technical Area	Publication Details	Published
Krios II-Titan Krios II at Diamond	Architecture of the outer-membrane core complex from a conjugative type IV secretion system Himani Amin , Aravindan Ilangovan , Tiago R. D. Costa Nature Communications 12 DOI: 10.1038/s41467-021-27178-8 Diamond Proposal Number(s): [18659] Open Access Show Abstract ▼ Abstract: Conjugation is one of the most important processes that bacteria utilize to spread antibiotic resistance genes among bacterial populations. Interbacterial DNA transfer requires a large double membrane-spanning nanomachine called the type 4 secretion system (T4SS) made up of the inner-membrane complex (IMC), the outer-membrane core complex (OMCC) and the conjugative pilus. The iconic F plasmid-encoded T4SS has been central in understanding conjugation for several decades, however atomic details of its structure are not known. Here, we report the structure of a complete conjugative OMCC encoded by the pED208 plasmid from E. coli, solved by cryo-electron microscopy at 3.3 Å resolution. This 2.1 MDa complex has a unique arrangement with two radial concentric rings, each having a different symmetry eventually contributing to remarkable differences in protein stoichiometry and flexibility in comparison to other OMCCs. Our structure suggests that F-OMCC is a highly dynamic complex, with implications for pilus extension and retraction during conjugation.	Dec 2021
Krios I-Titan Krios I at Diamond	Cryo-EM structure of a relaxase reveals the molecular basis of DNA unwinding during bacterial conjugation Aravindan Ilangovan , Christopher W. M. Kay , Sandro Roier , Hassane El Mkami , Enrico Salvadori , Ellen L. Zechner , Giulia Zanetti , Gabriel Waksman Cell DOI: 10.1016/j.cell.2017.04.010 Diamond Proposal Number(s): [13264, 15608] Open Access Show Abstract ▼ Abstract: Relaxases play essential roles in conjugation, the main process by which bacteria exchange genetic material, notably antibiotic resistance genes. They are bifunctional enzymes containing a trans-esterase activity, which is responsible for nicking the DNA strand to be transferred and for covalent attachment to the resulting 5′-phosphate end, and a helicase activity, which is responsible for unwinding the DNA while it is being transported to a recipient cell. Here we show that these two activities are carried out by two conformers that can both load simultaneously on the origin of transfer DNA. We solve the structure of one of these conformers by cryo electron microscopy to near-atomic resolution, elucidating the molecular basis of helicase function by relaxases and revealing insights into the mechanistic events taking place in the cell prior to substrate transport during conjugation.	Apr 2017
I02-Macromolecular Crystallography I04-Macromolecular Crystallography	Structural basis for native agonist and synthetic inhibitor recognition by the Pseudomonas aeruginosa quorum sensing regulator PqsR (MvfR) Aravindan Ilangovan , Matthew Fletcher , Giordano Rampioni , Christian Pustelny , Kendra Rumbaugh , Stephan Heeb , Miguel Cámara , Alex Truman , Siri Ram Chhabra , Jonas Emsley , Paul Williams Plos Pathogens 9 (7) DOI: 10.1371/journal.ppat.1003508 PMID: 23935486 Diamond Proposal Number(s): [6388] Open Access Show Abstract ▼ Abstract: Bacterial populations co-ordinate gene expression collectively through quorum sensing (QS), a cell-to-cell communication mechanism employing diffusible signal molecules. The LysR-type transcriptional regulator (LTTR) protein PqsR (MvfR) is a key component of alkyl-quinolone (AQ)-dependent QS in Pseudomonas aeruginosa. PqsR is activated by 2-alkyl-4-quinolones including the Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4(1H)-quinolone), its precursor 2-heptyl-4-hydroxyquinoline (HHQ) and their C9 congeners, 2-nonyl-3-hydroxy-4(1H)-quinolone (C9-PQS) and 2-nonyl-4-hydroxyquinoline (NHQ)	Jul 2013

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