  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.
