Research Interest: Structural studies of virus assembly Our lab uses the bacterial virus T4 to explore problems in cell biology related to control of shape and size of subcellular organelles. Our research is aimed at understanding more fully the shape and size determining mechanisms in morphogenesis using bacteriophages as an experimental system. We are interested in the molecular explanations for how head length and tail length are regulated as well as the way in which DNA is organized within the viral capsid. Bacteriophage T4 packages DNA by a "headful" mechanism: size of the capsid determine the amount of DNA. Mutations in the major capsid protein gene alter the head size and the amount of DNA packaged. Recent developments in the electrophoretic methods of DNA separation have made possible accurate length measurements of large, intact viral molecules. We have applied the method of rotating field gel electrophoresis to the DNA contained within normal T4 and capsid size variants produced by gene 23 mutations, and have found that there is a strong preference for certain DNA lengths that can be explained by the theory of icosahedral surface lattice geometry developed by Caspar and Klug, as modified for bacteriophage T4 by Moody and Aebi. This result suggests that head length is determined by a "vernier" mechanism that is a critical component of the DNA packaging system. We are pursuing evidence to prove this hypothesis.
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