The adsorption protein of bacteriophage fd and its neighbour minor coat protein build a structural entity

Abstract

The adsorption protein g3p and another minor coat protein, g6p, are located at one end of the filamentous bacteriophage fd [Grant, R. A., Lin, T. C., Konigsberg, W. E. & Webster, R. E. (1981) J. Biol. Chem. 256,. Both proteins, representing the proximal tip, were detached as an entity by a technique that allowed for gentle solubilization. Disrupting the phage particle with the detergent sodium deoxycholate and chloroform dissociates the major coat protein g8p, frees the phage DNA, but leaves g3p and g6p associated with each other. The g3p-g6p complex, which we termed the adsorption complex, and an oligomeric form of g3p with lower molecular mass were isolated and purified by gel-filtration chromatography in the presence of deoxycholate. These different oligomeric structures of g3p showed a different mobility in non-denaturing polyacrylamidegel electrophoresis. Both forms were also found in non-denaturing polyacrylamide-gel electrophoresis from deoxycholate-and Triton-X-100-solubilized phage without prior chromatographic separation. The two oligomeric forms of g3p are composed of two g3p polypeptide chains in the case of the low-molecular-mass species, and four g3p and four g6p polypeptide chains for the adsorption complex.

Filamentous phages: masters of a microbial sharing economy

“…Once the entirety of the phage DNA is coated in the major capsid protein, it must be released from the inner membrane and capped with the minor capsid proteins pIII and pVI, which form a stable complex at the base of the virion . If pIII of pVI is deleted, the virion cannot be released from the host cell and the filament continues to grow integrating multiple copies of the phage DNA into the growing filament .…”

Expanding the Versatility of Phage Display II: Improved Affinity Selection of Folded Domains on Protein VII and IX of the Filamentous Phage

“…( B ) In the wt phage there is about 2,700 copies of pVIII and approximately 3–5 copies each of the four proteins pIII, pVI, pVII and pIX, which are found at each tip of the virion [4], [35]. The virion size depends on the genome size at approx.…”

Precipitation of filamentous bacteriophages for their selective recovery in primary purification

“…Precipitations were by 4% (w/v) PEG 6,000, 2% (w/v) PEG 6,000–135 mM NaCl, 2% (w/v) PEG 6,000–25 mM and isoelectric precipitation, pH 4.3. The band observed at 60 kDa in precipitate samples corresponded to the “pIII” bacteriophage coat protein 31. All other coat proteins were below the minimum resolving size of the gel.…”

“…In Figure 6A, SDS‐PAGE analysis showed similar performance patterns to that observed for DNA, although a component of the bacteriophages was visible in precipitated samples: the band observed at 60 kDa corresponded to the “pIII” bacteriophage coat protein. Although the actual molecular weight of pIII is 42.6 kDa, it is known to run to the 60 kDa level 31. All other coat proteins were below the 20 kDa size limit of the gel.…”