Phage bacteriophage

Fig. 4. Construction of recombinant phage in vectors derived from bacteriophage lambda where E represents the enzyme EcoRl. Other terms are defined...

The number of helical turns in these structures is larger than those found so far in two-sheet p helices. The pectate lyase p helix consists of seven complete turns and is 34 A long and 17-27 A in diameter (Figure 5.30) while the p-helix part of the bacteriophage P22 tailspike protein has 13 complete turns. Both these proteins have other stmctural elements in addition to the P-helix moiety. The complete tailspike protein contains three intertwined, identical subunits each with the three-sheet p helix and is about 200 A long and 60 A wide. Six of these trimers are attached to each phage at the base of the icosahedral capsid. 

Certain strains of Escherichia coli can be stimulated by irradiation with a moderate dose of ultraviolet (UV) light to stop normal growth and start producing bacteriophages that eventually lyse the bacterium. Bacteria of these so-called lysogenic strains carry the DNA of the phage integrated into their own... 

Figure 8.1 A region of DNA in the related bacteriophages lambda, 434, and P22 that controls the switch for synthesis of new phage particles. Two structural genes are involved in this switch one coding for a repressor protein and one coding for the Cro protein. Between these genes there is an operator region (OR) that contains three protein binding sites—ORl, OR2, and OR3.

The renaturation rate of DNA is an excellent indicator of the sequence complexity of DNA. For example, bacteriophage T4 DNA contains about 2 X 10 nucleotide pairs, whereas Escherichia coli DNA possesses 4.64 X 10 . E. coli DNA is considerably more complex in that it encodes more information. Expressed another way, for any given amount of DNA (in grams), the sequences represented in an E. coli sample are more heterogeneous, that is, more dissimilar from one another, than those in an equal weight of phage T4 DNA. Therefore, it will take the E. coli DNA strands longer to find their complementary partners and reanneal. This situation can be analyzed quantitatively. 

Murialdo, H., 1991. Bacteriophage lambda DNA maturation and packaging. Annual Review of Biochemistry 60 125-153. Review of the biochemi.stry of packaging DNA into A phage heads. 

A bacteriophage (or phage) is a vims, made up of aDNA or RNA core and a protein coat that may infect bacteria. 

FIG. 1 Monolayer of T7 phage heads. Cryoelectron micrograph of tailless mutant of T7 bacteriophage. Bar 50 nm. (From Ref. 42. Copyright 1997 Cell Press.)... 

Viruses are discussed more fully elsewhere (Chapter 3). However, there are certain groups of viruses, called bacteriophages (phages), which can attack bacteria. This attack involves the injechon of viral DNA into baeterial eells which then proceed to make new virus particles and destroy eells. Some viruses, known as temperate viruses, do not cause this catastrophic event when they infect their host, but can pass genetic material from one cell to another. 

Bacteriophages, or as they are more sin tly termed, phages, are vimses that have bacteria as their host cells. The name was first given by D Herelle to an agent which he found could produce lysis of the dysentery bacillus Shigella shiga. D Herelle was convinced... 

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