9EX7

Cryo-EM structure of the E. coli BrxX methyltransferase in complex with Ocr

Summary for 9EX7

• Entry DOI: 10.2210/pdb9ex7/pdb
• EMDB information: 50032
• Descriptor: Adenine-specific methyltransferase BrxX, Protein Ocr, MAGNESIUM ION, ... (4 entities in total)
• Functional Keywords: methyltransferase, phage defense, brex, dna-binding, transferase
• Biological source: Escherichia coli; More
• Total number of polymer chains: 4
• Total formula weight: 304341.73

Authors

Adams, M.C.,Ghilarov, D. (deposition date: 2024-04-05, release date: 2025-03-05, Last modification date: 2025-07-09)

Primary citation

Drobiazko, A.,Adams, M.C.,Skutel, M.,Potekhina, K.,Kotovskaya, O.,Trofimova, A.,Matlashov, M.,Yatselenko, D.,Maxwell, K.L.,Blower, T.R.,Severinov, K.,Ghilarov, D.,Isaev, A.
Molecular basis of foreign DNA recognition by BREX anti-phage immunity system.
Nat Commun, 16:1825-1825, 2025

PubMed Abstract: Anti-phage systems of the BREX (BacteRiophage EXclusion) superfamily rely on site-specific epigenetic DNA methylation to discriminate between the host and invading DNA. We demonstrate that in Type I BREX systems, defense and methylation require BREX site DNA binding by the BrxX (PglX) methyltransferase employing S-adenosyl methionine as a cofactor. We determined 2.2-Å cryoEM structure of Escherichia coli BrxX bound to target dsDNA revealing molecular details of BREX DNA recognition. Structure-guided engineering of BrxX expands its DNA specificity and dramatically enhances phage defense. We show that BrxX alone does not methylate DNA, and BREX activity requires an assembly of a supramolecular BrxBCXZ immune complex. Finally, we present a cryoEM structure of BrxX bound to a phage-encoded inhibitor Ocr that sequesters BrxX in an inactive dimeric form. We propose that BrxX-mediated foreign DNA sensing is a necessary first step in activation of BREX defense.

PubMed: 39979294
DOI: 10.1038/s41467-025-57006-2

Experimental method

ELECTRON MICROSCOPY (2.91 Å)