title: Challenging packaging limits and infectivity of phage λ.
abstract: The terminase motors of bacteriophages have been shown to be among the strongest active machines in the biomolecular world, being able to package several tens of kilobase pairs of viral genome into a capsid within minutes. Yet, these motors are hindered at the end of the packaging process by the progressive buildup of a force-resisting packaging associated with already packaged DNA. In this experimental work, we raise the issue of what sets the upper limit on the length of the genome that can be packaged by the terminase motor of phage λ and still yield infectious virions and the conditions under which this can be efficiently performed. Using a packaging strategy developed in our laboratory of building phage λ from scratch, together with plaque assay monitoring, we have been able to show that the terminase motor of phage λ is able to produce infectious particles with up to 110% of the wild-type λ-DNA length. However, the phage production rate, and thus the infectivity, decreased exponentially with increasing DNA length and was a factor of 10(3) lower for the 110% λ-DNA phage. Interestingly, our in vitro strategy was still efficient in fully packaging phages with DNA lengths as high as 114% of the wild-type length, but these viruses were unable to infect bacterial cells efficiently. Further, we demonstrated that the phage production rate is modulated by the presence of multivalent ionic species. The biological consequences of these findings are discussed.
authors: Department of Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, Box 124, SE-221 00, Lund, Sweden.
authors: Elmar
authors: E
authors: Nurmemmedov
authors: Martin
authors: M
authors: Castelnovo
authors: Elizabeth
authors: E
authors: Medina
authors: Carlos Enrique
authors: CE
authors: Catalano
authors: Alex
authors: A
authors: Evilevitch
mesh_terms: D010582:Bacteriophage lambda / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D042003:DNA Packaging; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D019562:Viral Load; D010948:Viral Plaque Assay; D019065:Virus Assembly
chemical_list: D004706:Endodeoxyribonucleases; C030894:terminase