Molecular interactions between the constituents of small ribosomal   subunit
  Availability of high-resolution crystal structures of ribosomal subunits of different species opens a route to investigate about molecular interactions between its constituents and stabilization strategy. Structural analysis of the small ribosomal subunit shows that primary binder proteins are mainly employed in stabilizing the folded ribosomal RNA by their high negative free energy of association, where tertiary binders mainly help to stabilize protein-protein interfaces. Secondary binders perform both the functions. Conformational changes of prokaryotic and eukaryotic ribosomal proteins due to complexation with 16S ribosomal RNA are linearly correlated with their RNA-interface area and free energy of association. The proteins having long extensions buried within ribosomal RNA have more flexible structures than those found on the subunit surface. Thermus thermophilus ribosomal proteins undergo high conformational changes compared to those of Escherichia coli, assuring structural stability at high temperature environment. The general stabilization strategy of ribosomal protein-RNA interfaces is shown, where high interface polarity ensures high surface density of Hydrogen bonds even with low base/backbone ratio. Polarity is regulated in evolutionary strategy of ribosomal proteins. Thus, the habitat environmental conditions of the two species sweet up their ribosomal protein-RNA interfaces to alter its physical parameters in order of stabilization. 
Saurav Mallik and Sudip Kundu
q-bio.BM