Non-Canonical Conformations of DNA Strands Containing Guanine and Adenine
AbstraktThe review describes non-canonical conformers that are adopted by DNA strands containing alternating guanine (G) - adenine (A) or related repeats. The following factors stand behind their remarkably extensive conformational polymorphism extending beyond the Watson and Crick DNA model: a) many possibilities of GA and GG pairing; b) strong interactions between large purine bases including interstrand base stacking overlap and other stabilizing interactions, e.g., intercalation of bases into the parent duplex; c) almost equal stabilities of quanine and adenine in the anti and syn orientations around the glycosidic bonds. It is suggested that the (G+A)-rich sequences perform their biological functions through the unique conformational properties. This adds a further argument for an imagination that DNA does not only carry out its biological functions through being a passive template for transcription.