6PPU

Cryo-EM structure of AdnAB-AMPPNP-DNA complex

Summary for 6PPU

• Entry DOI: 10.2210/pdb6ppu/pdb
• EMDB information: 20440 20446 20447
• Descriptor: UvrD/REP helicase, ATP-dependent DNA helicase (UvrD/REP), DNA (29-MER), ... (5 entities in total)
• Functional Keywords: dna, dna binding protein, dna binding protein-dna complex, dna binding protein/dna
• Biological source: Mycobacterium smegmatis (strain ATCC 700084 / mc(2)155); More
• Total number of polymer chains: 3
• Total formula weight: 216031.51

Authors

Jia, N.,Unciuleac, M.,Shuman, S.,Patel, D.J. (deposition date: 2019-07-08, release date: 2019-11-20, Last modification date: 2024-03-20)

Primary citation

Jia, N.,Unciuleac, M.C.,Xue, C.,Greene, E.C.,Patel, D.J.,Shuman, S.
Structures and single-molecule analysis of bacterial motor nuclease AdnAB illuminate the mechanism of DNA double-strand break resection.
Proc.Natl.Acad.Sci.USA, 116:24507-24516, 2019

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.

PubMed: 31740608
DOI: 10.1073/pnas.1913546116

Experimental method

ELECTRON MICROSCOPY (3.5 Å)