Biochemistry - Adaptive recognition by nucleic acid aptamers

Nucleic acid molecules play crucial roles in diverse biological processes i ncluding the storage, transport, processing, and expression of the genetic information. Nucleic acid aptamers are selected in vitro from Libraries con taining random sequences of up to a few hundred nucleotides. Selection is b ased on the ability to bind ligand molecules with high affinity and specifi city. Three-dimensional structures have been determined at high resolution for a number of aptamers in complex with their cognate ligands. Structures of aptamer complexes reveal the key molecular interactions conferring speci ficity to the aptamer-ligand association, including the precise stacking of flat moieties, specific hydrogen bonding, and molecular shape complementar ity. These basic principles of discriminatory molecular interactions in apt amer complexes parallel recognition events central to many cellular process es involving nucleic acids.