CONFORMATIONAL PROPERTIES OF DNA STRANDS CONTAINING GUANINE AND ADENINE

The review describes non-canonical conformers that are adopted by DNA strands containing alternating guanine (G) - adenine (A) or related re peats. The following factors stand behind their remarkably extensive c onformational polymorphism extending beyond the Watson and Crick DNA m odel: a) many possibilities of GA and GG pairing; b) strong interactio ns between large purine bases including interstrand base stacking over lap and other stabilizing interactions, e.g., intercalation of bases i nto the parent duplex; c) almost equal stabilities of quanine and aden ine in the anti and syn orientations around the glycosidic bonds. It i s suggested that the (G+A)-rich sequences perform their biological fun ctions through the unique conformational properties. This adds a furth er argument for an imagination that DNA does not only carry out its bi ological functions through being a passive template for transcription.