Jj. Blackstock et al., Shape of ocr, the gene 0.3 protein of bacteriophage T7: Modeling based on light scattering experiments, BIOCHEM, 40(33), 2001, pp. 9944-9949
Ocr, the first protein expressed by bacteriophage T7, inhibits type I DNA r
estriction enzymes by preventing them from binding to DNA. This inhibition
allows the phage to successfully infect the host. The shape of ocr is model
ed on the basis of static and dynamic light scattering measurements. The st
atic light scattering data confirm previous observations that ocr exists in
solution as a dimer. The diffusion constant determined by dynamic light sc
attering indicates a nonspherical shape of the ocr dimer. Hydrodynamic mode
ls of ellipsoids are presented, and it is argued that ocr is best described
by a prolate ellipsoid with dimensions of 10.4 run by 2.6 mn. The size and
shape predicted by this model are consistent with ocr acting as a mimic of
the DNA structure bound by type I restriction enzymes.