Gene regulation is essential for all life-forms since it increases the versatility and adaptability of an organism by allowing the cell to express a protein as and when needed. Each life form adopts its own way of regulating its genetic machinery. Riboswitches, which are composed entirely of RNA and control gene expression, have recently been discovered in a variety of organisms. These RNA elements have special response to small molecules(ligands) and they regulate the concentration of these by regulating their bio-chemical synthesis or pathways. Hence they are named as "switches". They have all the attributes of protein-based sensors but are less complex and smaller than their protein counterparts. In this work, thermodynamics and homology modelingare used to find new, putative riboswitches in bacteria, archaea and eukaryotes. In the much-studied model organism B.subtilis subtilis, almost all type of riboswitches are present. In other prokaryotes also, many types of riboswitches are detected, butin the case of eukaryotes only TPP riboswitch is found up till now. The two representative archaea studied show putative TPP, FMN and Purine riboswitches. TPP riboswitch is most widely present in case of prokaryotes and perhaps also in eukaryotes.
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