Filamentous phages replication

Many aspects of DNA replication in filamentous phages are similar to that of < >X 174. The unique property, release without cell killing, can be briefly discussed. The release from the cell occurs by a budding process in which the virus particle is always released from the cell with the end containing the A protein first. Interestingly, the orientation of the virus particle across the cell membrane is the same for its entry and exit from the cell. There is no accumulation of intracellular virus particles the assembly of mature virus particles occurs on the inner cell membrane and virus assembly is coupled with the budding process. 

Another viral chromosome that can be used as a vector is that of the filamentous phage Ml3. The M13 chromosome is a single-stranded DNA molecule which when inserted into the bacterial host replicates outside the bacterial chromosome in the cytoplasm. The virus is then reassembled and released from the bacterial cell without cell lysis. 

Tyrosine residues can also be used to describe the structoe and the dynamics of a protein. Single stranded DNA binding protein modulates DNA replication and repair, transcription, translation, regulation and recombination. However, while most of SSB proteins activate DNA replication, e.g. Escherichia coli SSB and 029 SSB, some SSBs such as those of filamentous phages Ml 3, are inhibitory. 

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. 

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