{Reference Type}: Journal Article
{Title}: Biophysical and structural characterization of a multifunctional viral genome packaging motor.
{Author}: Prokhorov NS;Davis CR;Maruthi K;Yang Q;Sherman MB;Woodson M;White MA;Miller LM;Jarrold MF;Catalano CE;Morais MC;
{Journal}: Nucleic Acids Res
{Volume}: 52
{Issue}: 2
{Year}: 2024 Jan 25
{Factor}: 19.16
{DOI}: 10.1093/nar/gkad1135
{Abstract}: The large dsDNA viruses replicate their DNA as concatemers consisting of multiple covalently linked genomes. Genome packaging is catalyzed by a terminase enzyme that excises individual genomes from concatemers and packages them into preassembled procapsids. These disparate tasks are catalyzed by terminase alternating between two distinct states-a stable nuclease that excises individual genomes and a dynamic motor that translocates DNA into the procapsid. It was proposed that bacteriophage λ terminase assembles as an anti-parallel dimer-of-dimers nuclease complex at the packaging initiation site. In contrast, all characterized packaging motors are composed of five terminase subunits bound to the procapsid in a parallel orientation. Here, we describe biophysical and structural characterization of the λ holoenzyme complex assembled in solution. Analytical ultracentrifugation, small angle X-ray scattering, and native mass spectrometry indicate that 5 subunits assemble a cone-shaped terminase complex. Classification of cryoEM images reveals starfish-like rings with skewed pentameric symmetry and one special subunit. We propose a model wherein nuclease domains of two subunits alternate between a dimeric head-to-head arrangement for genome maturation and a fully parallel arrangement during genome packaging. Given that genome packaging is strongly conserved in both prokaryotic and eukaryotic viruses, the results have broad biological implications.