Download MendeleyStructures and single-molecule analysis of bacterial motor nuclease AdnAB illuminate the mechanism of DNA double-strand break resection.
Jia, N., Unciuleac, M.C., Xue, C., Greene, E.C., Patel, D.J., Shuman, S.(2019) Proc Natl Acad Sci U S A 116: 24507-24516
- PubMed: 31740608
- DOI: https://doi.org/10.1073/pnas.1913546116
- Primary Citation of Related Structures:
6PPJ, 6PPR, 6PPU - PubMed Abstract:
Mycobacterial AdnAB is a heterodimeric helicase-nuclease that initiates homologous recombination by resecting DNA double-strand breaks (DSBs). The AdnA and AdnB subunits are each composed of an N-terminal motor domain and a C-terminal nuclease domain. Here we report cryoelectron microscopy (cryo-EM) structures of AdnAB in three functional states: in the absence of DNA and in complex with forked duplex DNAs before and after cleavage of the 5' single-strand DNA (ssDNA) tail by the AdnA nuclease. The structures reveal the path of the 5' ssDNA through the AdnA nuclease domain and the mechanism of 5' strand cleavage; the path of the 3' tracking strand through the AdnB motor and the DNA contacts that couple ATP hydrolysis to mechanical work; the position of the AdnA iron-sulfur cluster subdomain at the Y junction and its likely role in maintaining the split trajectories of the unwound 5' and 3' strands. Single-molecule DNA curtain analysis of DSB resection reveals that AdnAB is highly processive but prone to spontaneous pausing at random sites on duplex DNA. A striking property of AdnAB is that the velocity of DSB resection slows after the enzyme experiences a spontaneous pause. Our results highlight shared as well as distinctive properties of AdnAB vis-à-vis the RecBCD and AddAB clades of bacterial DSB-resecting motor nucleases.
Organizational Affiliation:
Structural Biology Program, Sloan Kettering Institute, New York, NY 10065.
