Structural highlights
Function[TERM_BPP22] Involved in the phage DNA-packaging initiation process. Packaging of DNA occurs by cutting headful-sized fragments in a sequential manner from a DNA concatemer. To initiate this process, protein gp3 recognizes a signal sequence: the pac site. Publication Abstract from PubMedPackaging of viral genomes into empty procapsids is powered by a large DNA-packaging motor. In most viruses, this machine is composed of a large (L) and a small (S) terminase subunit complexed with a dodecamer of portal protein. Here we describe the 1.75 A crystal structure of the bacteriophage P22 S-terminase in a nonameric conformation. The structure presents a central channel approximately 23 A in diameter, sufficiently large to accommodate hydrated B-DNA. The last 23 residues of S-terminase are essential for binding to DNA and assembly to L-terminase. Upon binding to its own DNA, S-terminase functions as a specific activator of L-terminase ATPase activity. The DNA-dependent stimulation of ATPase activity thus rationalizes the exclusive specificity of genome-packaging motors for viral DNA in the crowd of host DNA, ensuring fidelity of packaging and avoiding wasteful ATP hydrolysis. This posits a model for DNA-dependent activation of genome-packaging motors of general interest in virology. Small Terminase Couples Viral DNA Binding to Genome-Packaging ATPase Activity.,Roy A, Bhardwaj A, Datta P, Lander GC, Cingolani G Structure. 2012 Jul 3. PMID:22771211[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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