[Quaternary structure of the ribosomal 30S subparticle: the model and its experimental verification]

In considering the structure of the ribosomal 30S subparticle from Escherichia coli we have assumed that : 1) all or almost all the proteins in the 30S subparticle are compact and globular as has been shown for isolated proteins S4, S7, S8, S15 and S16 in solution [Serdyuk I. N., Zaccai G. and Spirin A. S. (1978) FEBS Letters, 94, 349-352]; 2) RNA within the 30S subparticle has the same specific V-like or Y-like shape demonstrated for the isolated 16S RNA in a compact conformation [Vasiliev V. D., Selivanova O. M. and Koteliansky V. E. (1978) FEBS Letters, 95, 273-276]. On the basis of this assumption and numerous data published on the mutual localization of ribosomal proteins, we have constructed a model of the quaternary structure of the ribosomal 30S subparticle. We have tested the model by comparing the theoretically calculated curves of neutron and X-ray scattering at different contrasts with the corresponding experimental scattering curves of the E. coli 30S subparticles and have found that they coincide. The calculated scattering curves of several previously published three-dimensional diagrams of protein topography in the 30S subparticle do not agree with experiment.