Filamentous phages structure

Marvin, D.A. 1998. Filamentous phage structure, infection and assembly. Curr. Opin. Struct. Biol. 8, 150-158. 

S Cabilly. The basic structure of filamentous phage and its use in the display of combinatorial peptide libraries. Mol Biotechnol 12 143-148, 1999. 

At the start of the infectious process, lambda phage contacts a nutrient transport protein (the maltose transporter) on the membrane of the . colL Without this membrane-bound protein, the phage cannot infect the . cell. At the start of the infectious process, filamentous phage contacts the pilus of the . coli. Without this extracellular structure, the phage cannot infect the E. coli. When lambda phage reproduces, it causes the bacterial cdl to burst, and the . coli is killed. When filamentous phage reproduces, it leaves the . edi in a harmless budding process, and the E. coli survives. 

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 12 Structure of M13 filamentous phage (a) Schematic diagram of the stmcture of Ml3 denoting the location and population of each coat protein subunit encapsulating a single, circular strand of DNA. (b) Portion of repeating array of pVin coat protein subunits as determined by fiber X-ray studies. Individual pVIII coat protein molecules are represented as ribbons of a-helices. (Reproduced with permission from Ref. 47. Elsevier, 2001.)...

The tail is a complex multicomponent structure which often ends in tail fibres. In filamentous phages, the nucleic acid, which is in an extended helical form, is contained within the capsid. 

Fig. 15.2 Schematic diagram showing the structure of the filamentous phage and its different modes of display. (A) Filamentous phages are rod-hke viruses with a circular ssDNA genome of about 6.4kb. The tube-hke capsid is composed of several thousand copies (up to 2700) of tightly packed major coat protein pVin, capped by five copies of pill and pVI on one end and five copies of pVn and pIX on the opposite end. (B) Phage display hbraries can be displayed on the surface of the Ff phage by fusion to the different capsid proteins.

Makowski, L. 1994. Phage display structure, assembly and engineering of filamentous bacteriophage. ( hit. Opin. Struct. Biol. 4, 225—230. 

Holliger P, Riechmann L, A conserved infection pathway for filamentous bacteriophages is suggested by the structure of the membrane penetration domain of the minor coat protein g3p from phage fd, Structure, 5 265-275, 1997. 

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