摘要

共轭转座驱动多种细菌病原体出现多药耐药性，但其机制表征不佳。 Tn1549接合转座子对用于严重耐药感染的抗生素万古霉素产生抗性。在这里，我们提出了与圆形转座子DNA中间体复合的Tn1549的保守Y-转座酶的四个高分辨率结构。这些结构揭示了各个转座步骤，并解释了具体DNA变形和切割机制如何使DNA链交换具有绝对最小的同源性要求。这似乎独特地允许Tn916样接合转座子绕过DNA同源性并插入不同的基因组位点，从而扩大基因转移。我们进一步揭示了一种结构调控机制，其防止在发现合适的靶DNA之前过早切割转座子DNA并产生干扰转座酶-DNA结构以阻断转座的肽拮抗剂。我们的研究结果揭示了共轭转座的机制原理，可以帮助控制抗生素抗性基因的传播。

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 severedrug-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.

https://www.ncbi.nlm.nih.gov/pubmed/29551265