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From Proteopedia
CryoEM structure of the TnsC(1-503)-TnsD(1-318)-DNA complex in a 7:2:1 stoichiometry from E. coli Tn7 bound to ATPgS and ADP
Structural highlights
FunctionTNSC_ECOLX TnsC binds non-specifically to DNA in the presence of ATP. It is required for Tn7 transposition. TnsABC + TnsD promote high-frequency insertion of Tn7 into a specific target site known as att-Tn7 whereas TnsABC + TnsE promote low-frequency insertion into many different sites. Publication Abstract from PubMedThe Tn7 family of transposons is notable for its highly regulated integration mechanisms, including programmable RNA-guided transposition. The targeting pathways rely on dedicated target selection proteins from the TniQ family and the AAA+ adaptor TnsC to recruit and activate the transposase at specific target sites. Here, we report the cryoelectron microscopy (cryo-EM) structures of TnsC bound to the TniQ domain of TnsD from prototypical Tn7 and unveil key regulatory steps stemming from unique behaviors of ATP- versus ADP-bound TnsC. We show that TnsD recruits ADP-bound dimers of TnsC and acts as an exchange factor to release one protomer with exchange to ATP. This loading process explains how TnsC assembles a heptameric ring unidirectionally from the target site. This unique loading process results in functionally distinct TnsC protomers within the ring, providing a checkpoint for target immunity and explaining how insertions at programmed sites precisely occur in a specific orientation across Tn7 elements. Assembly of the Tn7 targeting complex by a regulated stepwise process.,Shen Y, Krishnan SS, Petassi MT, Hancock MA, Peters JE, Guarne A Mol Cell. 2024 Jun 20;84(12):2368-2381.e6. doi: 10.1016/j.molcel.2024.05.012. , Epub 2024 Jun 3. PMID:38834067[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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