4beb
MUTANT (K220E) OF THE HSDR SUBUNIT OF THE ECOR124I RESTRICTION ENZYME IN COMPLEX WITH ATP
Structural highlights
FunctionT1R1_ECOLX The restriction (R) subunit of a type I restriction enzyme that recognizes 5'-GAAN(7)RTCG-3' and cleaves a random distance away. Subunit R is required for both nuclease and ATPase activities, but not for modification (Probable) (PubMed:12654995). After locating an unmethylated recognition site, the enzyme complex serves as a molecular motor that translocates DNA in an ATP-dependent manner until a collision occurs that triggers cleavage (Probable). The enzyme undergoes major structural changes to bring the motor domains into contact with DNA, allowing DNA translocation. This prevents DNA access to the catalytic domains of both the R and M subunits, preventing both restriction and methylation (PubMed:32483229).[1] [2] [3] [4] Publication Abstract from PubMedType I restriction-modification enzymes are multifunctional heteromeric complexes with DNA cleavage and ATP-dependent DNA translocation activities located on motor subunit HsdR. Functional coupling of DNA cleavage and translocation is a hallmark of the Type I restriction systems that is consistent with their proposed role in horizontal gene transfer. DNA cleavage occurs at nonspecific sites distant from the cognate recognition sequence, apparently triggered by stalled translocation. The X-ray crystal structure of the complete HsdR subunit from E. coli plasmid R124 suggested that the triggering mechanism involves interdomain contacts mediated by ATP. In the present work, in vivo and in vitro activity assays and crystal structures of three mutants of EcoR124I HsdR designed to probe this mechanism are reported. The results indicate that interdomain engagement via ATP is indeed responsible for signal transmission between the endonuclease and helicase domains of the motor subunit. A previously identified sequence motif that is shared by the RecB nucleases and some Type I endonucleases is implicated in signaling. Functional coupling of duplex translocation to DNA cleavage in a type I restriction enzyme.,Csefalvay E, Lapkouski M, Guzanova A, Csefalvay L, Baikova T, Shevelev I, Bialevich V, Shamayeva K, Janscak P, Kuta Smatanova I, Panjikar S, Carey J, Weiserova M, Ettrich R PLoS One. 2015 Jun 3;10(6):e0128700. doi: 10.1371/journal.pone.0128700., eCollection 2015. PMID:26039067[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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