Filamentous phages sites

Thioredoxin (1,2) are small (M. 11-12,000) ubiquitous redox proteins with two half-cystine residues in the conserved active site structure Trp-Cys-Gly-Pro-Cys. The oxidized form Trx-S2 is reduced by NADPH and thioredoxin-reductase the reduced rorm Trx(SH)2 is a powerful protein disulfide oxido-reductase which regulatesthe activity of enzymes by thiol redox control it serves as hydrogen donor for various reductive enzymes such as ribonucleotide reductase or enzymes reducing sulfate or methionine sulfoxide. Also, Trx(SH)2 is essential for phage T7 DNA replication as a subunit of T7 DNA polymerase and assembly of filamentous phages (fl and M13), at least in E, ooti. 

Figure 5.16 Illustration of the manner by which the virion of a filamentous single-stranded phage (such as M13 or fd) leaves an infected cell without lysis. The A protein passes first through the membrane at a site on the membrane where coat protein molecules have first become imbedded. The intracellular circular DNA is coated with dimers of another protein, gp5, which is displaced by coat protein as the DNA passes through the intact membrane.

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