Bacteriophage P22 portal protein is part of the gauge that regulates packing density of intravirion DNA

Casjens, Sherwood; Wyckoff, Elizabeth E.; Hayden, Melody; Sampson, Laura; Eppler, Kathryn; Randall, Steven; Moreno, Elena T.; Serwer, Philip

doi:10.1016/0022-2836(92)90469-z

Cited by 106 publications

(80 citation statements)

References 77 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The portal protein is also involved in determination of the endonucleolytic cleavage that terminates DNA packaging. This role, initially described for phages that encapsidate DNA by a headful mechanism (Casjens et al ., 1992;Tavares et al ., 1992), was recently extended to bacteriophage l which terminates DNA packaging by a sequence-specific cleavage (Cue and Feiss, 1997).…”

Section: Introductionmentioning

confidence: 99%

The high‐resolution functional map of bacteriophage SPP1 portal protein

Isidro

Santos

Henriques

et al. 2003

Molecular Microbiology

View full text Add to dashboard Cite

SummaryAn essential component in the assembly of nucleocapsids of tailed bacteriophages and of herpes viruses is the portal protein that is located at the unique vertex of the icosahedral capsid through which DNA movements occur. A library of mutations in the bacteriophage SPP1 portal protein (gp6) was generated by random mutagenesis of gene 6 . Screening of the library allowed identification of 67 single amino acid substitutions that impair portal protein function. Most of the mutations cluster within stretches of a few amino acids in the gp6 carboxyl-terminus. The mutations were divided into five classes according to the step of virus assembly that they impair: (1) production of stable gp6; (2) interaction of gp6 with the minor capsid protein gp7; (3) incorporation of gp6 in the procapsid structure; (4) DNA packaging; and (5) sizing of the packaged DNA molecule. Most of the mutations fell in classes 3 and 4. This is the first high-resolution functional map of a portal protein, in which its function at different steps of viral assembly can be directly correlated with specific regions of its sequence. The work provides a framework for the understanding of central processes in the assembly of viruses that use specialized portals to govern entry and exit of DNA from the viral capsid.

show abstract

Section: Introductionmentioning

confidence: 99%

The high‐resolution functional map of bacteriophage SPP1 portal protein

Isidro

Santos

Henriques

et al. 2003

Molecular Microbiology

View full text Add to dashboard Cite

show abstract

“…The portal works in conjunction with the motor, but its exact role is unclear. Various models such as the portal acting as a valve, DNA cruncher, or packaging sensor have been proposed (8,9,10,38,43).…”

mentioning

confidence: 99%

Portal-Large Terminase Interactions of the Bacteriophage T4 DNA Packaging Machine Implicate a Molecular Lever Mechanism for Coupling ATPase to DNA Translocation

Hegde

Padilla-Sanchez

Draper

et al. 2012

J Virol

View full text Add to dashboard Cite

DNA packaging by double-stranded DNA bacteriophages and herpesviruses is driven by a powerful molecular machine assembled at the portal vertex of the empty prohead. The phage T4 packaging machine consists of three components: dodecameric portal (gp20), pentameric large terminase motor (gp17), and 11-or 12-meric small terminase (gp16). These components dynamically interact and orchestrate a complex series of reactions to produce a DNA-filled head containing one viral genome per head. Here, we analyzed the interactions between the portal and motor proteins using a direct binding assay, mutagenesis, and structural analyses. Our results show that a portal binding site is located in the ATP hydrolysis-controlling subdomain II of gp17. Mutations at key residues of this site lead to temperature-sensitive or null phenotypes. A conserved helix-turn-helix (HLH) that is part of this site interacts with the portal. A recombinant HLH peptide competes with gp17 for portal binding and blocks DNA translocation. The helices apparently provide specificity to capture the cognate prohead, whereas the loop residues communicate the portal interaction to the ATPase center. These observations lead to a hypothesis in which a unique HLH-portal interaction in the symmetrically mismatched complex acts as a lever to position the arginine finger and trigger ATP hydrolysis. Transiently connecting the critical parts of the motor; subdomain I (ATP binding), subdomain II (controlling ATP hydrolysis), and C-domain (DNA movement), the portal-motor interactions might ensure tight coupling between ATP hydrolysis and DNA translocation.T ailed bacteriophages and herpesviruses use powerful ATPdriven machines to package their genomes into preformed capsid shells (36). They generate forces greater than 60 pN, ϳ20 times that of myosin motor, in order to compact a highly negatively charged, relatively rigid double-stranded DNA (dsDNA) to near-crystalline density (ϳ500 g/ml) (22, 39). The phage T4 employs one of the fastest and most powerful packaging machines reported to date. Packaging at a rate of up to ϳ2,000 bp/s, the T4 machine is estimated to generate twice the power (ϳ5,000 kW/ m 3 ) of an automobile engine (12, 36). The T4 packaging machine consists of three components ( Fig. 1): (i) an empty prohead containing a dodecameric portal protein, gp20 (25, 38); (ii) a pentameric large terminase motor protein, gp17 (5, 24, 42); and (iii) an 11-or 12-mer small terminase regulatory protein, gp16 (2, 24, 35). The cone-shaped portal links the head to the motor and DNA, with its wider end inside the capsid and the narrower end protruding outside. It has a central channel with a diameter of ϳ35 Å, through which DNA is threaded into the capsid. The portal works in conjunction with the motor, but its exact role is unclear. Various models such as the portal acting as a valve, DNA cruncher, or packaging sensor have been proposed (8,9,10,38,43).Five molecules of gp17 assemble on the portal into a packaging motor (Fig. 1). gp17 consists of an N-terminal ATPase domai...

show abstract

“…The contraction of T3 shells to sub-phage R E has previously been observed both during analysis of T3 DNA packaging intermediates 84 and after the expulsion of packaged DNA from shells that initially had a complete genome. 85 Thus, shell contraction, in general, is not surprising. But, loss of shell subunits is an alternative explanation for size decrease and this alternative explanation has not been empirically excluded for Figure 5.…”

Section: Managing Of Neoplasmsmentioning

confidence: 99%

Enhancing and initiating phage-based therapies

et al. 2014

Self Cite

View full text Add to dashboard Cite

D rug development has typically been a primary foundation of strategy for systematic, long-range management of pathogenic cells. However, drug development is limited in speed and flexibility when response is needed to changes in pathogenic cells, especially changes that produce drug-resistance. The high replication speed and high diversity of phages are potentially useful for increasing both response speed and response flexibility when changes occur in either drug resistance or other aspects of pathogenic cells. We present strategy, with some empirical details, for (1) using modern molecular biology and biophysics to access these advantages during the phage therapy of bacterial infections, and (2) initiating use of phage capsid-based drug delivery vehicles (DDVs) with procedures that potentially overcome both drug resistance and other present limitations in the use of DDVs for the therapy of neoplasms. The discussion of phage therapy includes (a) historical considerations, (b) changes that appear to be needed in clinical tests if use of phage therapy is to be expanded, (c) recent work on novel phages and its potential use for expanding the capabilities of phage therapy and (d) an outline for a strategy that encompasses both theory and practice for expanding the applications of phage therapy. The discussion of DDVs starts by reviewing current work on DDVs, including work on both liposomal and viral DDVs. The discussion concludes with some details of the potential use of permeability constrained phage capsids as DDVs.

show abstract

Bacteriophage P22 portal protein is part of the gauge that regulates packing density of intravirion DNA

Cited by 106 publications

References 77 publications

The high‐resolution functional map of bacteriophage SPP1 portal protein

The high‐resolution functional map of bacteriophage SPP1 portal protein

Portal-Large Terminase Interactions of the Bacteriophage T4 DNA Packaging Machine Implicate a Molecular Lever Mechanism for Coupling ATPase to DNA Translocation

Enhancing and initiating phage-based therapies

Contact Info

Product

Resources

About