7sjr | pdb_00007sjr

Cryo-EM structure of AdnA-AdnB(W325A) in complex with DNA and AMPPNP

spinqualitylabelsall models 7sjr, resolution 3.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 7sjr is a 3 chain structure with sequence from Mycolicibacterium smegmatis. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 3.8Å Ligands: ANP, MG, SF4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function I7FZ56_MYCS2 Publication Abstract from PubMed Mycobacterial AdnAB is a heterodimeric helicase-nuclease that initiates homologous recombination by resecting DNA double-strand breaks. The AdnB subunit hydrolyzes ATP to drive single-nucleotide steps of 3'-to-5' translocation of AdnAB on the tracking DNA strand via a ratchet-like mechanism. Trp325 in AdnB motif III, which intercalates into the tracking strand and makes a pi stack on a nucleobase 5' of a flipped-out nucleoside, is the putative ratchet pawl without which ATP hydrolysis is mechanically futile. Here, we report that AdnAB mutants wherein Trp325 was replaced with phenylalanine, tyrosine, histidine, leucine, or alanine retained activity in ssDNA-dependent ATP hydrolysis but displayed a gradient of effects on DSB resection. The resection velocities of Phe325 and Tyr325 mutants were 90% and 85% of the wild-type AdnAB velocity. His325 slowed resection rate to 3% of wild-type and Leu325 and Ala325 abolished DNA resection. A cryo-EM structure of the DNA-bound Ala325 mutant revealed that the AdnB motif III peptide was disordered and the erstwhile flipped out tracking strand nucleobase reverted to a continuous base-stacked arrangement with its neighbors. We conclude that pi stacking of Trp325 on a DNA nucleobase triggers and stabilizes the flipped-out conformation of the neighboring nucleoside that underlies formation of a ratchet pawl. Structure-activity relationships at a nucleobase-stacking tryptophan required for chemomechanical coupling in the DNA resecting motor-nuclease AdnAB.,Warren GM, Meir A, Wang J, Patel DJ, Greene EC, Shuman S Nucleic Acids Res. 2022 Jan 25;50(2):952-961. doi: 10.1093/nar/gkab1270. PMID:34967418 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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