Mycobacterial Lhr is a DNA damage-inducible superfamily 2 helicase that uses adenosine triphosphate (ATP) hydrolysis to drive unidirectional 3′-to-5′ translocation along single-stranded DNA (ssDNA) and to unwind RNA:DNA duplexes en route. ATPase, translocase and helicase activities are encompassed within the N-terminal 856-amino acid segment. The crystal structure of Lhr-(1–856) in complex with AMPPNP•Mg²⁺ and ssDNA defines a new helicase family. The enzyme comprises two N-terminal RecA-like modules, a winged helix (WH) domain and a unique C-terminal domain. The 3′ ssDNA end binds in a crescent-shaped groove at the interface between the first RecA domain and the WH domain and tracks 5′ into a groove between the second RecA and C domains. A kissing interaction between the second RecA and C domains forms an aperture that demarcates a putative junction between the loading strand tail and the duplex, with the first duplex nucleoside bookended by stacking on Trp597. Intercalation of Ile528 between nucleosides of the loading strand creates another bookend. Coupling of ATP hydrolysis to RNA:DNA unwinding is dependent on Trp597 and Ile528, and on Thr145 and Arg279 that contact phosphates of the loading strand. The structural and functional data suggest a ratchet mechanism of translocation and unwinding coupled to ATP-driven domain movements.

中文翻译：

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结合至ssDNA追踪链的分枝杆菌3'至5'RNA：DNA解旋酶Lhr的结构突出了新型细菌解旋酶家族的独特特征

分枝杆菌Lhr是一种可诱导DNA损伤的超家族2解旋酶，它使用三磷酸腺苷（ATP）水解来驱动单链DNA（ssDNA）的单向3'至5'易位，并在途中解开RNA：DNA双链体。ATP酶，转位酶和解旋酶活性涵盖在N端856个氨基酸区段内。Lhr-（1-856）与AMPPNP•Mg ^2+的复合物的晶体结构ssDNA定义了一个新的解旋酶家族。该酶包含两个N端RecA样模块，一个带翼的螺旋（WH）结构域和一个唯一的C端结构域。3'ssDNA末端在第一RecA结构域和WH结构域之间的界面处的月牙形凹槽中结合，并在第二RecA和C结构域之间的凹槽中跟踪5'。第二个RecA和C结构域之间的亲吻相互作用形成了一个孔，该孔界定了负载链尾部和双链体之间的假定连接，第一双链体核苷通过堆叠在Trp597上而被固定。Ile528在装载链的核苷之间的插入产生另一个书夹。ATP水解与RNA：DNA的解偶联取决于Trp597和Ile528，以及与负载链的磷酸盐接触的Thr145和Arg279。