Mandal Maumita, Breaker Ronald R
Department of Molecular, Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, Connecticut 06520-8103, USA.
Nat Struct Mol Biol. 2004 Jan;11(1):29-35. doi: 10.1038/nsmb710. Epub 2003 Dec 29.
A class of riboswitches that recognizes guanine and discriminates against other purine analogs was recently identified. RNAs that carry the consensus sequence and structural features of guanine riboswitches are located in the 5' untranslated region (UTR) of numerous prokaryotic genes, where they control the expression of proteins involved in purine salvage and biosynthesis. We report that three representatives of this riboswitch class bind adenine with values for apparent dissociation constant (apparent K(d)) that are several orders of magnitude lower than those for binding guanine. Because preference for adenine is attributable to a single nucleotide substitution, the RNA most likely recognizes its ligand by forming a Watson-Crick base pair. In addition, the adenine riboswitch associated with the ydhL gene of Bacillus subtilis functions as a genetic 'on' switch, wherein adenine binding causes a structural rearrangement that precludes formation of an intrinsic transcription terminator stem.
最近发现了一类识别鸟嘌呤并区分其他嘌呤类似物的核糖开关。携带鸟嘌呤核糖开关共有序列和结构特征的RNA位于众多原核基因的5'非翻译区（UTR），在那里它们控制参与嘌呤补救和生物合成的蛋白质的表达。我们报告说，这类核糖开关的三个代表与腺嘌呤结合，其表观解离常数（表观K(d)）值比与鸟嘌呤结合的值低几个数量级。由于对腺嘌呤的偏好归因于单个核苷酸取代，RNA很可能通过形成沃森-克里克碱基对来识别其配体。此外，与枯草芽孢杆菌ydhL基因相关的腺嘌呤核糖开关起到遗传“开启”开关的作用，其中腺嘌呤结合会导致结构重排，从而阻止形成内在转录终止子茎。
