Structural basis for altering the stability of homologous RNAs from a mesophilic and a thermophilic bacterium

Correlating changes in stability (K_Mg) to folding cooperativity (Hill constant, •) and the number of new and altered interactions for E. coli S-domain mutants (□). Mutations in a local structure can increase stability (P9 + P11 and J11/12 + P14) but are insufficient to change folding cooperativity. Simultaneous mutations in more than one local structure can increase folding cooperativity but do not gain additional stability as defined by the K_Mg value.