pH Dependence of the Chemical Labeling of Thermus thermophilus HB8 Ribosomes

摘要

SMTA labeling can be extended to pH between 6.0 and 9.0. Ribosomal proteins show distinct labeling patterns. (1) Extent reactivity is predictable by inspection of crystal structures. (2) Native structure is preserved across the pH range. (3) Changing buffers or ionic strength does not denature ribosomes. Proteins showing little change in reactivity from pH 6.6 to 8.3 are: (1) Exposed to solution and flexible (e. g. L7/L12). (2) Buried in rRNA (e. g. L27). Proteins showing large changes in reactivity have exposed lysines that: (1) Interact with adjacent carboxylates. (2) Interact with the rRNA backbone. Tertiary and quaternary interactions can be disrupted by pH changes (1) Structure alterations are non-denaturing. (2) Structure alterations localize to flexible regions in a complex.