6mii
From Proteopedia
Crystal structure of minichromosome maintenance protein MCM/DNA complex
Structural highlights
FunctionMCM_SACS2 Presumptive replicative helicase. Has ATPase and DNA helicase activities. The latter preferentially melts 5'-tailed oligonucleotides and is stimulated by the SSB protein (single-stranded DNA binding protein). The active ATPase sites in the MCM ring are formed through the interaction surfaces of two neighboring subunits such that a critical structure of a conserved arginine finger motif is provided in trans relative to the ATP-binding site of the Walker A box of the adjacent subunit. The helicase function is proposed to use a partially sequential mode of ATP hydrolysis; the complex appears to tolerate multiple catalytically inactive subunits.[1] Publication Abstract from PubMedThe DNA translocation activity of the minichromosome maintenance (MCM) complex powers DNA strand separation of the replication forks of eukaryotes and archaea. Here we illustrate an atomic level mechanism for this activity with a crystal structure of an archaeal MCM hexamer bound to single-stranded DNA and nucleotide cofactors. Sequence conservation indicates this rotary mechanism is fully possible for all eukaryotes and archaea. The structure definitively demonstrates the ring orients during translocation with the N-terminal domain leading, indicating that the translocation activity could also provide the physical basis of replication initiation where a double-hexamer idly encircling double-stranded DNA transforms to single-hexamers that encircle only one strand. In this mechanism, each strand binds to the N-terminal tier of one hexamer and the AAA+ tier of the other hexamer such that one ring pulls on the other, aligning equivalent interfaces to enable each hexamer to pull its translocation strand outside of the opposing hexamer. DNA translocation mechanism of the MCM complex and implications for replication initiation.,Meagher M, Epling LB, Enemark EJ Nat Commun. 2019 Jul 15;10(1):3117. doi: 10.1038/s41467-019-11074-3. PMID:31308367[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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