title: Small terminase couples viral DNA binding to genome-packaging ATPase activity.
abstract: Packaging 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 Å crystal structure of the bacteriophage P22 S-terminase in a nonameric conformation. The structure presents a central channel ∼23 Å 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.
authors: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA.
authors: Ankoor
authors: A
authors: Roy
authors: Anshul
authors: A
authors: Bhardwaj
authors: Pinaki
authors: P
authors: Datta
authors: Gabriel C
authors: GC
authors: Lander
authors: Gino
authors: G
authors: Cingolani
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000595:Amino Acid Sequence; D017100:Bacteriophage P22 / Q000201:enzymology* / Q000502:physiology; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004279:DNA, Viral / Q000737:chemistry; D004706:Endodeoxyribonucleases / Q000737:chemistry*; D006868:Hydrolysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D014764:Viral Proteins / Q000737:chemistry*; D019065:Virus Assembly
chemical_list: D004279:DNA, Viral; D021122:Protein Subunits; D014764:Viral Proteins; D000255:Adenosine Triphosphate; D004706:Endodeoxyribonucleases; C030894:terminase