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.

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 cite journal | last = Barrick | first = JE | coauthors = Corbino KA, Winkler WC, Nahvi A, Mandal M, Collins J, Lee M, Roth A, Sudarsan N, Jona I, Wickiser JK, Breaker RR | year = 2004 | title = New RNA motifs suggest an expanded scope for riboswitches in bacterial genetic control | journal = Proc Natl Acad Sci USA | volume = 101 | pages = 6421–6426 | pmid = 15096624 | doi = 10.1073/pnas.0308014101] . Examples of the conserved M-box RNA structure occur upstream of each of the three major families of Mg²⁺ transporters in various bacterial species cite journal | last = Dann | first = CE 3rd | coauthors = Wakeman CA, Sieling CL, Baker SC, Irnov I, Winkler WC | year = 2007 | title = Structure and mechanism of a metal-sensing regulatory RNA | journal = Cell | volume =130 | pages = 878–92 | pmid = 17803910 | doi = 10.1016/j.cell.2007.06.051] . 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.

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External links

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* [http://www.pdb.org/pdb/explore.do?structureId=2QBZ Protein Data Bank: M-Box Structure]