6n0s

Publication Abstract from PubMed

McrBC is a conserved modification-dependent restriction system that in Escherichia coli specifically targets foreign DNA containing methylated cytosines. Crystallographic data show that the N-terminal domain of Escherichia coli McrB binds substrates via a base flipping mechanism. This region is poorly conserved among the plethora of McrB homologs, suggesting that other species may use alternative binding strategies and/or recognize different targets. Here we present the crystal structure of the N-terminal domain from Stayphlothermus marinus McrB (Sm3-180) at 1.92 A, which adopts a PUA-like EVE fold that is closely related to the YTH and ASCH RNA binding domains. Unlike most PUA-like domains, Sm3-180 binds DNA and can associate with different modified substrates. We find the canonical 'aromatic cage' binding pocket that confers specificity for methylated bases in other EVE/YTH domains is degenerate and occluded in Sm3-180, which may contribute to its promiscuity in target recognition. Further structural comparison between different PUA-like domains identifies motifs and conformational variations that correlate with the preference for binding either DNA or RNA. Together these data have important implications for PUA-like domain specificity and suggest a broader biological versatility for the McrBC family than previously described.

The N-terminal domain of Staphylothermus marinus McrB shares structural homology with PUA-like RNA binding proteins.,Hosford CJ, Adams MC, Niu Y, Chappie JS J Struct Biol. 2020 Sep 1;211(3):107572. doi: 10.1016/j.jsb.2020.107572. Epub, 2020 Jul 8. PMID:32652237^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.