title: A point mutation in the Nul gene of bacteriophage lambda facilitates phage growth in Escherichia coli with himA and gyrB mutations.
abstract: A mutant of lambda was isolated that grows in the Escherichia coli himA delta/gyrB-him320(Ts) double mutant at 42 degrees C; conditions which are non-permissive for wild-type lambda growth. The responsible mutation, ohm1, alters the 40th codon of the Nul reading frame. The Nul and A gene products comprise the terminase protein which cleaves concatameric DNA into unit-length phage genomes during DNA packaging. The Nul-ohm1 gene product acts in trans to support lambda growth in the double himA/gyrB mutant, and lambda cos154 growth in the single himA mutant. The observation that an alteration in Nul suppresses the inhibition of growth in the double himA/gyrB mutant implicates DNA gyrase, as well as integration host factor, in the DNA:protein interactions that occur at the initiation of packaging.
authors.affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109.
authors.forename: A E
authors.initials: AE
authors.lastname: Granston
authors.forename: D M
authors.initials: DM
authors.lastname: Alessi
authors.forename: L J
authors.initials: LJ
authors.lastname: Eades
authors.forename: D I
authors.initials: DI
authors.lastname: Friedman
mesh_terms: D010582:Bacteriophage lambda / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D004250:DNA Topoisomerases, Type II / Q000235:genetics; D004706:Endodeoxyribonucleases / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D005796:Genes; D005814:Genes, Viral; D005816:Genetic Complementation Test; D009154:Mutation
chemical_list: D004706:Endodeoxyribonucleases; C030894:terminase; D004250:DNA Topoisomerases, Type II