Conjugative transposition drives the emergence of multidrug resistance in diverse bacterial pathogens, yet the mechanisms are poorly characterized. The Tn1549 conjugative transposon propagates resistance to the antibiotic vancomycin used for severe drug-resistant infections. Here, we present four high-resolution structures of the conserved Y-transposase of Tn1549 complexed with circular transposon DNA intermediates. The structures reveal individual transposition steps and explain how specific DNA distortion and cleavage mechanisms enable DNA strand exchange with an absolute minimum homology requirement. This appears to uniquely allow Tn916-like conjugative transposons to bypass DNA homology and insert into diverse genomic sites, expanding gene transfer. We further uncover a structural regulatory mechanism that prevents premature cleavage of the transposon DNA before a suitable target DNA is found and generate a peptide antagonist that interferes with the transposase-DNA structure to block transposition. Our results reveal mechanistic principles of conjugative transposition that could help control the spread of antibiotic resistance genes.

中文翻译：

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转座酶-DNA复杂结构揭示了抗生素抗性的共轭转座机制。

共轭转座驱动了多种细菌病原体中多药耐药性的出现，但其机理尚不清楚。Tn1549共轭转座子可传播对用于严重耐药性感染的抗生素万古霉素的耐药性。在这里，我们提出了与环状转座子DNA中间体复合的保守的Tn1549 Y转座酶的高分辨率结构。该结构揭示了各个转座步骤，并解释了特定的DNA畸变和切割机制如何以绝对最小的同源性要求实现DNA链交换。这似乎独特地允许Tn916样共轭转座子绕过DNA同源性并插入不同的基因组位点，扩大基因转移。我们进一步揭示了一种结构调节机制，该机制可防止转座子DNA的过早裂解，然后找到合适的靶DNA并产生干扰转座酶DNA结构的蛋白拮抗剂，从而阻止转座。我们的结果揭示了共轭转座的机械原理，可以帮助控制抗生素抗性基因的传播。