Architecture of the Tn7 Posttransposition Complex: An Elaborate Nucleoprotein Structure

摘要: Four transposition proteins encoded by the bacterial transposon Tn7, TnsA, TnsB, TnsC, and TnsD, mediate its site- orientation-specific insertion into chromosomal site attTn7. To establish which Tns are actually present in transpososome that executes DNA breakage joining, we have determined nucleoprotein product of transposition, posttransposition complex (PTC), using fluorescently labeled proteins. All four required PTC also find Tn7 ends paired protein-protein contacts between bound to ends. Quantification relative amounts fluorescent indicates oligomers TnsC transposition. High-resolution footprinting attTn7Colon, two colonsTn7 revealed about 350 bp on attTn7 contact seven binding sites for component transposase specifically binds mediates 3' end occupied PTC. However, protection pattern closest different from observed with TnsB alone, likely reflecting pairing their interaction target necessary activation joining steps. We observe extensive sequences alternative structures substrate imposed TnsD maintained