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Cryo-EM structure of ATP-DNA-MuB filaments
Structural highlights
FunctionTARGB_BPMU Selects the target DNA sites for transposition. Recruits DDE-recombinase A to the target sites and catalytically activates it. Displays non-specific DNA-binding properties. Polymerizes as helical filaments around the DNA. Coating of the DNA by the target DNA activator B might play a role in favoring target-primed replication over integration. Prevents self-integration into an integrated copy of the viral genome. This mechanism is called target immunity and is achieved by two mechanisms: first, the target DNA activator B dissociates from the viral genome ends upon interaction in cis with DDE-recombinase A, which makes the viral genome ends a poor target for new insertions. Second, the interior of the viral genome may also ne protected from integration events by the target DNA activator B being strongly bound throughout the whole viral genome.[1] [2] [3] [4] [5] [6] [7] [8] Publication Abstract from PubMedMuB is a non-specific DNA-binding protein and AAA+ ATPase that significantly influences the DNA transposition process of bacteriophage Mu, especially in target DNA selection for transposition. While studies have established the ATP-dependent formation of MuB filament as pivotal to this process, the high-resolution structure of a full-length MuB protomer and the underlying molecular mechanisms governing its oligomerization remain elusive. Here, we use cryo-EM to obtain a 3.4-A resolution structure of the ATP(+)-DNA(+)-MuB helical filament, which encapsulates the DNA substrate within its axial channel. The structure categorizes MuB within the initiator clade of the AAA+ protein family and precisely locates the ATP and DNA binding sites. Further investigation into the oligomeric states of MuB show the existence of various forms of the filament. These findings lead to a mechanistic model where MuB forms opposite helical filaments along the DNA, exposing potential target sites on the bare DNA and then recruiting MuA, which stimulates MuB's ATPase activity and disrupts the previously formed helical structure. When this happens, MuB generates larger ring structures and dissociates from the DNA. Elucidating the Architectural dynamics of MuB filaments in bacteriophage Mu DNA transposition.,Zhao X, Gao Y, Gong Q, Zhang K, Li S Nat Commun. 2024 Jul 31;15(1):6445. doi: 10.1038/s41467-024-50722-1. PMID:39085263[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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