Other phages

Display on lambda phages has been described with two major coat proteins the gpV tail protein [23, 24] and the gpD head protein [25, 26]. Both proteins accept C-terminal fusions, which offers alternative systems for displaying cDNA libraries. A high level of display is possible as demonstrated by the total modification of gpV [27] and gpD [25] proteins. The structure of gpD has been solved recently [28] this should help the design of optimal display vectors. 

Display on T4 phage has been reported on a minor coat protein called fibritin [29] and on two outer capsid proteins, HOC and SOC [30, 31]. HOC and SOC accept, respectively, N-terminal and C-terminal fusions. High levels of full-length protein display have been obtained with both proteins between 10 and 40 copies of a protein of 183 amino acid residues were expressed per phage particle [32]. 

A disadvantage of these systems is probably the lower efficiency and convenience of cloning libraries of DNA molecules. This difficulty has been alleviated by using a Cre-loxP recombination strategy the fusion gene is cloned in a small plasmid and then efficiently recombined in vivo into the phage [25], 

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Phage P22 apparently requires the presence of the dideoxyhexosyl group, since an abequose-deficient LPS was not cleaved by the phage enzyme (33). On the other hand, two other phages, 28B and 36, with endoglycosidase activity against the L-Rha (al->-3)D-Gal linkage were able to cleave the abequose-deficient LPS (36). 

The phage library used in most of our selections for cell ligands displays a 20mer peptide at the amino-terminus of the minor coat protein pill (19). We have selected peptides from other phage display libraries (5), including the Ph.D. 12-mer library available from New England Biolabs(MJM and KCB unpublished results). 

Amplification of Jumping libraries is carried out as described for other phage libraries (25). 

The discovery of 5-hydroxymethylcytosine had not been announced at the time the analyses of the DNA of T5 and the tentative figures for T3 were obtained. Hence, base reported as cytosine for these phages may be identical with the new pyrimidine. Confirmation of the presence of the new base in the other phages of the T series will be eagerly awaited. 

No information is yet available on other phages except that Siddiqi et al. (287) have stated that lysine is present in T6 to the extent of 3.45 X 10 y per active particle. 

SP6 RNA Pol has been conventionally purified from phage SP6-infected S. typhimurium LT2. Compared with other phage (T3 and T7) polymerases, SP6 RNA Pol is significantly more stable and easier to purify. SP6 RNA Pol is now produced from the gene cloned in a pBR322 vector (pSR3) and overexpressed in E. coli BL21. 

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