Small Angle Scattering Study of the Structure and Organization of RNAs and Protein of Brome Mosaic Virus (BMV) Capsid Protein

Brome mosaic virus (BMV) viron is a model system that has a small icosahedral capsid protein (CP) shell. It is well known that BMV is plant virus which is a member of the alpha virus-like superfamily group. These viruses have genetic material and nucleic acids (RNA) with a segmented positive-strand RNA that offers high levels of RNA synthesis and virus production in plants. BMV CP tightly regulates the packaging of its RNAs into the inner core of the capsid while maintaining an outer protein shell coat. Small angle neutron scattering (SANS) and small angle X- ray scattering (SAXS) were applied to study the size, shape and protein-RNAs organization of BMV CP. BMV capsid protein and buffer solution containing a D2O/H2O mixture was used to enhance the contrast of the material for neutron scattering measurements. The pair distance distribution P(r) of BMV CP from the indirect Fourier transform of scattering spectrum was able to illustrate the differences in the distribution of materials, signifying RNAs packing, and protein in the BMV CP. The extracted parameter from P(r) shows that the BMV CP is about 260Å in diameter and is composed of RNA with ∼ 74Å core radiuses and coated protein shell of thickness 56Å. The contribution of RNAs core, protein shell was estimated by simulation. The contribution due to interference of core and shell called cross term was also extracted from simulation