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9.B.78 The Minor Capsid Protein, gp7, of Bacillus subtilis Phage SPP1 (gp7) Family

Gp7 is a minor capsid protein of the Bacillus subtilis bacteriophage SPP1. Homologous proteins are found in numerous phages. Deletion of gene 7 from the SPP1 genome yielded a mutant phage (SPP1del7) with reduced burst-size. SPP1del7 infections led to normal assembly of virus particles whose morphology, DNA and protein composition was undistinguishable from wild-type virions. However, only approximately 25% of the viral particles that lack gp7 were infectious (Vinga et al., 2006). SPP1del7 particles caused a reduced depolarization of the B. subtilis membrane in infection assays suggesting a defect in virus genome traffic to the host cell. A higher number of SPP1del7 DNA ejection events led to abortive release of DNA to the culture medium when compared with wild-type infections. DNA ejection in vitro showed that no detectable gp7 is co-ejected with the SPP1 genome and that its presence in the virion correlated with anchoring of released DNA to the phage particle. The release of DNA from wild-type phages was slower than that from SPP1del7 suggesting that gp7 controls DNA exit from the virion. This feature is proposed to play a central role in supporting correct routing of the phage genome from the virion to the cell cytoplasm (Vinga et al., 2006). Antiviral agents, BIT225, benzamine, amantadine and NN-DNJ all interact with a heptameric form of p7 (Dahl et al. 2017).

gp7 facilitates the transport reaction:

Phage DNA (phage particle) → Phage DNA (host cytoplasm)

References associated with 9.B.78 family:

Dahl, S., M.M. Kalita, and W.B. Fischer. (2017). Interaction of antivirals with a heptameric bundle model of the p7 protein of hepatitis C virus. Chem Biol Drug Des. [Epub: Ahead of Print] 29251816
Vinga, I., A. Dröge, A.C. Stiege, R. Lurz, M.A. Santos, R. Daugelavicius, and P. Tavares. (2006). The minor capsid protein gp7 of bacteriophage SPP1 is required for efficient infection of Bacillus subtilis. Mol. Microbiol. 61: 1609-1621. 16899078