Enteric Chromosomal Islands: DNA Packaging Specificity and Role of λ-like Helper Phage Terminase.

The phage-inducible chromosomal islands (PICIs) of Gram-negative bacteria are analogous to defective prophages that have lost the ability to propagate without the aid of a helper phage. PICIs have acquired genes that alter the genetic repertoire of the bacterial host, including supplying virulence factors. Recent work by the Penadés laboratory elucidates how a helper phage infection or prophage induction induces the island to excise from the bacterial chromosome, replicate, and become packaged into functional virions.

The product of the bacteriophage lambda W gene: purification and properties.

Gene W is one of the 10 genes that control the morphogenesis of the bacteriophage lambda head. The morpho genesis of the phage lambda head proceeds through the synthesis of an intermediate assembly called the prohead. This is an empty shell into which the bacteriophage DNA is introduced--packaged--by the phage enzyme DNA terminase.

The bacteriophage lambda DNA packaging enzyme: identification of four structural domains of the gpNu1 subunit using limited proteolysis.

Lambda DNA terminase, the enzyme that cleaves virion-length chromosomes from multigenomic concatemers and packages them into the bacteriophage head, is composed of two subunits, gpNu1 and gpA. Direct determination of the structure of gpNu1, the smaller subunit, has not been possible because of its insolubility in aqueous solutions. Therefore, to identify smaller and potentially water-soluble domains of gpNu1, we analyzed the nature of the products obtained by limited digestion of the protein with several proteases.

Thermodynamic and functional characterization of protein W from bacteriophage lambda. The three C-terminal residues are critical for activity.

Gene product W (gpW), the head-tail joining protein from bacteriophage lambda, provides a fascinating model for studying protein interactions. Composed of only 68 residues, it must interact with at least two other proteins in the phage, and probably with DNA. To study the structural and functional properties of gpW, plasmids were constructed expressing gpW with hexahistidine tag sequences at either the N or C terminus.

Mutations in the terminase genes of bacteriophage lambda that bypass the necessity for FI.

DNA maturation in bacteriophage lambda is the process by which the concatemeric precursor DNA is cleaved at sites called cos to generate mature lambda DNA molecules. These DNA molecules are then packaged into procapsids, the empty capsid precursors. The enzyme that catalyses these events is lambda DNA terminase.