Bacteriophages – a molecular “rifle” Sol M. Gruner, Cornell University , DMR 0936384

1. Bacteriophages – a molecular “rifle”Sol M. Gruner, Cornell University, DMR 0936384 Intellectual Merit: Bacteriophages are viruses which infect bacteria. Many of them consist of a rigid icosahedral capsid containing the phage's genetic material attached to a tail which penetrates the bacterial wall during the infection process. A complex structure known as the "portal" connects the tail and the capsid, and is required both to load the capsid with DNA (or RNA) and to mediate its injection into the host bacterium. In combination with previously determined X-ray and electron microscopy structures, the Cingolani group study helps construct a detailed model of the dodecameric portal of P22, showing that during injection of DNA into a bacterium, the long barrel domain stabilizes the linear momentum of the DNA as it is propelled along by the internal pressure in the capsid. Just as a rifle is more accurate and powerful than a pistol, DNA ejection through a long tube is more effective than through a short tube. Model of double-stranded DNA inside P22 portal protein, with four protein monomers removed to show the interior of the channel. This long channel serves like a “rifle” to direct the linear momentum of the DNA (downwards) through the bacterium wall during viral infection. A.S. Olia, P.E. Prevelige Jr., and G. Cingolani; "Three-dimensional Structure of a Viral Genome-delivery Portal Vertex", Nature Struct. 7 Mol. Biol.18, 597-603 (2011) CHESS DMR-0936384 2011_1