Phages

Phacomp system PH Adjustment Phages Phaltan Phanodorm Pharaceuticals PHARM Pharmaceutical... 

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

Fig. 9. Mutagenesis by a synthetic oligonucleotide of a cloned sequence available in single-stranded form (a) single-stranded M13 template containing uracil (U) residues (b) double-stranded product, uracil residues are not mutagenic (c) strong selection for M13 phages containing mutation of interest (23).

Fig. 5. Generation of mutants using single-stranded DNA. After cloning the target gene into M13, the phage is propagated in the E. coll dut, ung strain of E.

Commercial fermentation groups usually maintain different strains of cultures suitable for production so that phage attacks can be thwarted by substituting a nonsusceptible culture. After a period of time for the phage to dissipate, it may be possible to return the most desirable production strain. 

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.

Cro, by contrast, acts purely as a repressor. When it is bound to its high-affinity site at OR3, it prevents repressor synthesis by obstructing the access of polymerase to the left-hand promoter. In the absence of repressor, RNA polymerase can bind to the Cro promoter, and Cro can be synthesized along with the early phage genes to its right. 

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