YkoK leader

The Ykok leader or M-box is a Mg2+-sensing RNA structure that controls the expression of Magnesium ion transport proteins in bacteria. It is a distinct structure to the Magnesium responsive RNA element.

ykoK leader
Predicted secondary structure and sequence conservation of ykoK
Identifiers
SymbolykoK
RfamRF00380
Other data
RNA typeCis-reg; riboswitch
Domain(s)Bacteria
SO0000233
PDB structuresPDBe

The Ykok leader was originally described as a conserved sequence with potential riboswitch function found upstream of the B. subtilis ykoK gene and genes with related functions in other bacteria.[1] Examples of the conserved M-box RNA structure occur upstream of each of the three major families of Mg2+ transporters (CorA, MgtE and MgtA/MgtB) in various bacterial species.[2]

The molecular structure of the M-box example upstream of the B. subtilis ykoK gene includes six bound Mg2+ ions. Biochemical studies indicate that this M-Box RNA compacts in the presence of Mg2+ and other divalent ions. This folding process appears to disrupt an antiterminator structure, and thereby allow a transcription terminator structure to form. As expected from this model, B. subtilis cells repress expression of a downstream reporter gene when grown in the presence of Mg2+. Therefore, the M-box appears to function as a genetic "off" switch that is important for maintaining Mg2+ homeostasis in bacteria.

  • A 3D representation of the Ykok leader. Structure of the M-box riboswitch aptamer domain from Bacillus subtilis.[2]

References
  1. Barrick, JE; Corbino KA; Winkler WC; Nahvi A; Mandal M; Collins J; Lee M; Roth A; Sudarsan N; Jona I; Wickiser JK; Breaker RR (2004). "New RNA motifs suggest an expanded scope for riboswitches in bacterial genetic control". Proc Natl Acad Sci USA. 101 (17): 6421–6426. doi:10.1073/pnas.0308014101. PMC 404060. PMID 15096624.
  2. Dann CE, Wakeman CA, Sieling CL, Baker SC, Irnov I, Winkler WC (2007). "Structure and mechanism of a metal-sensing regulatory RNA". Cell. 130 (5): 878–892. doi:10.1016/j.cell.2007.06.051. PMID 17803910.
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