Cryo-EM structure of a relaxase reveals the molecular basis of DNA unwinding during bacterial conjugation
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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.
Ilangovan , A , Kay , C W M , Roier , S , El Mkami , H , Salvadori , E , Zechner , E L , Zanetti , G & Waksman , G 2017 , ' Cryo-EM structure of a relaxase reveals the molecular basis of DNA unwinding during bacterial conjugation ' Cell , vol 169 , no. 4 , e12 , pp. 708-721 . DOI: 10.1016/j.cell.2017.04.010
© 2017 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
This work was supported by Wellcome Trust grant 098302 to G.W., a Royal Society Dorothy Hodgkin fellowship to G.Z. DH130048, and Austrian Science Fund (FWF) grants P24016 and W901 DK Molecular Enzymology to E.L.Z. S.R. is a BioTechMed-Graz PostDoc. H.E.M. and the EPR Facility at St Andrews are supported in part by Wellcome Trust grant 099149/Z/12/Z.
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