Polymorphism of bacteriophage T7

Irene S. Gabashvili, Saeed A. Khan, Shirley J. Hayes, Philip Serwer

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


For viruses made of nucleic acid and protein, the structure of the protein outer shell has, in the past, been found to be uniquely determined by the viral genome. However, here, non-denaturing agarose gel electrophoresis of bacteriophage T7 reveals two states of the mature T7 capsid; the conditions of growth are found to alter the population by T7 of these two electrophoretically defined states. Both states have been previously observed for a genetically altered T7 and they are observed here for wild-type T7. The average electrical surface charge density of a bacteriophage particle (δ) determines its state; the δ of particles in both states is negative. For a given condition of growth, the population of these two states is influenced by the extent to which the major T7 outer shell protein, p10A, is accompanied by its minor readthrough variant, p10B. Comparison of the two electrophoretic states reveals the following. (1) No difference in radius is present in the outer shell (± 2%). (2) As the pH of electrophoresis is either increased or decreased from neutrality, the state becomes more highly populated for which δ is greater in magnitude (state 1). By changing the pH, some T7 particles are made to change state. (3) Particles in state 1 adsorb less quickly to host cells than do the particles in the alternative state (state 2). This latter observation suggests the hypothesis that state 1 evolved to reduce the probability of re-initiating an infection when conditions are not favorable for growth. This hypothesis is supported by the observation that, as conditions of growth become apparently more unfavorable, progeny increasingly populate state 1.

Original languageEnglish (US)
Pages (from-to)658-667
Number of pages10
JournalJournal of Molecular Biology
Issue number3
StatePublished - Oct 31 1997


  • Agarose gel electrophoresis
  • Bacteriophage evolution
  • Bacteriophage structure
  • Two-dimensional electrophoresis

ASJC Scopus subject areas

  • Molecular Biology
  • Structural Biology


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