7pik
Cryo-EM structure of E. coli TnsB in complex with right end fragment of Tn7 transposon
Structural highlights
FunctionTNSB_ECOLX Sequence-specific, DNA-binding protein required for Tn7 transposition. Recognizes sequences necessary for recombination at both left and right ends of Tn7 and, together with TnsA, forms the transposase. TnsB executes the 5'-DNA strand breakage and joining reactions.[1] [2] Publication Abstract from PubMedTn7 is a bacterial transposon with relatives containing element-encoded CRISPR-Cas systems mediating RNA-guided transposon insertion. Here, we present the 2.7 A cryoelectron microscopy structure of prototypic Tn7 transposase TnsB interacting with the transposon end DNA. When TnsB interacts across repeating binding sites, it adopts a beads-on-a-string architecture, where the DNA-binding and catalytic domains are arranged in a tiled and intertwined fashion. The DNA-binding domains form few base-specific contacts leading to a binding preference that requires multiple weakly conserved sites at the appropriate spacing to achieve DNA sequence specificity. TnsB binding imparts differences in the global structure of the protein-bound DNA ends dictated by the spacing or overlap of binding sites explaining functional differences in the left and right ends of the element. We propose a model of the strand-transfer complex in which the terminal TnsB molecule is rearranged so that its catalytic domain is in a position conducive to transposition. Structural basis of transposon end recognition explains central features of Tn7 transposition systems.,Kaczmarska Z, Czarnocki-Cieciura M, Gorecka-Minakowska KM, Wingo RJ, Jackiewicz J, Zajko W, Poznanski JT, Rawski M, Grant T, Peters JE, Nowotny M Mol Cell. 2022 Jul 21;82(14):2618-2632.e7. doi: 10.1016/j.molcel.2022.05.005. , Epub 2022 Jun 1. PMID:35654042[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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