sentences:  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.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.The molecular structure of the M-box example upstream of the "B. subtilis" ykoK gene includes six bound Mg2+ ions.