We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
DNA Packaging by ƛ-Like Bacteriophages: Mutations Broadening the Packaging Specificity of Terminase, the ƛ-Packaging Enzyme.
- Authors
Feiss, Michael; Reynolds, Erin; Schrock, Morgan; Sippy, Jean
- Abstract
The DNA-packaging specificities of phages λ and 21 depend on the specific DNA interactions of the small terminase subunits, which have support helix-turn-recognition helix-wing DNA-binding motifs. λ-Terminase with the recognition helix of 21 preferentially packages 21 DNA. This chimeric terminase's ability to package lDNA is reduced ∼20-fold. Phage λ with the chimeric terminase is unable to form plaques, but pseudorevertants are readily obtained. Some pseudorevertants have trans-acting suppressors that change codons of the recognition helix. Some of these codons appear to remove an unfavorable basepair contact; others appear to create a novel nonspecific DNA contact. Helper-packaging experiments show that these mutant terminases have lost the ability to discriminate between λ and 21 during DNA packaging. Two cis-acting suppressors affect cosB, the small subunit's DNA-binding site. Each changes a cosB λ-specific base pair to a cosB21-specific base pair. These cosB suppressors cause enhanced DNA packaging by 21-specific terminase and reduce packaging by λ-terminase. Both the cognate support helix and turn are required for strong packaging discrimination. The wing does not contribute to cosB specificity. Evolution of packaging specificity is discussed, including a model in which λ- and 21-packaging specificities diverged from a common ancestor phage with broad packaging specificity.
- Subjects
BACTERIOPHAGES; DNA; GENETIC mutation; PATHOGENIC microorganisms; VIRUSES; NUCLEIC acids
- Publication
Genetics, 2010, Vol 184, Issue 1, p43
- ISSN
0016-6731
- Publication type
Article
- DOI
10.1534/genetics.109.108548