Magnesium controls aptamer-expression platform switching in the SAM-I riboswitch.

ABSTRACT: Investigations of most riboswitches remain confined to the ligand-binding aptamer domain. However, during the riboswitch mediated transcription regulation process, the aptamer domain and the expression platform compete for a shared strand. If the expression platform dominates, an anti-terminator helix is formed, and the transcription process is active (ON state). When the aptamer dominates, transcription is terminated (OFF state). Here, we use an expression platform switching experimental assay and structure-based electrostatic simulations to investigate this ON-OFF transition of the full length SAM-I riboswitch and its magnesium concentration dependence. Interestingly, we find the ratio of the OFF population to the ON population to vary non-monotonically as magnesium concentration increas

SUBMITTER: Roy S 

PROVIDER: S-EPMC6451092 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature