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

(A) Partial T1 nuclease digestion at an [Mg²⁺] where I and N are highly populated. T. thermophilus S-domain exhibits strongly contrasting patterns in the I and the N states. Some protection factors (PF = amount of cleavage product in I state divided by amount of cleavage product in N state normalized to the total amount of RNA in each lane) are indicated for comparison (number following semicolon). Numbering for both RNAs is according to the T. thermophilus sequence. (B) T1 cleavage at 0.05 or 0.1 mM Mg²⁺, where the I state predominates. (C) T1 cleavage at 1.6 mM Mg²⁺, where the N state predominates.