1j9i | pdb_00001j9i
STRUCTURE OF THE DNA BINDING DOMAIN OF THE GPNU1 SUBUNIT OF LAMBDA TERMINASE
Structural highlights
Function[TERS_LAMBD] Component of the terminase that processes and encapsidates viral genomes during virion assembly. The terminase is composed of two small and one large subunits. To initiate packaging, it binds a specific sequence called cos, at the junction of adjacent viral genomes in the concatemeric DNA substrate. Next, in a reaction stimulated by the presence of proheads and ATP but not requiring ATP hydrolysis, the terminase creates two nicks 12bp appart at the cos site, one on each stand. Terminase then separates the cohesive ends in a reaction requiring ATP hydrolysis. The heterotrimer remains bound to the left end of the genome to be packaged, forming a stable DNA-protein complex known as complex I. In a reaction facilitated by a viral assembly catalyst, gpFI, complex I binds a prohead, a preformed head shell precursor, to form complex II. In another packaging reaction requiring ATP hydrolysis, the DNA is translocated into the prohead until the next cos site on the concatemer reaches the packaging complex. At this time the downstream cos site is cut and the heterotrimer undocks from the DNA-filled head to remain bound to the left end of concatemer's next genome. The new heterotrimer-DNA complex I binds another prohead to continue the processive, polarized packaging of viral genomes. The terminase is dependent upon host integration host factor (ihfA/ihfB) for these activities.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedTerminase enzymes mediate genome "packaging" during the reproduction of DNA viruses. In lambda, the gpNu1 subunit guides site-specific assembly of terminase onto DNA. The structure of the dimeric DNA binding domain of gpNu1 was solved using nuclear magnetic resonance spectroscopy. Its fold contains a unique winged helix-turn-helix (wHTH) motif within a novel scaffold. Surprisingly, a predicted P loop ATP binding motif is in fact the wing of the DNA binding motif. Structural and genetic analysis has identified determinants of DNA recognition specificity within the wHTH motif and the DNA recognition sequence. The structure reveals an unexpected DNA binding mode and provides a mechanistic basis for the concerted action of gpNu1 and Escherichia coli integration host factor during assembly of the packaging machinery. Insights into specific DNA recognition during the assembly of a viral genome packaging machine.,de Beer T, Fang J, Ortega M, Yang Q, Maes L, Duffy C, Berton N, Sippy J, Overduin M, Feiss M, Catalano CE Mol Cell. 2002 May;9(5):981-91. PMID:12049735[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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