Two grooves that run the length of the DNA double helix. The major groove is 12 Angstroms wide, while the minor groove is 6 Angstroms wide. The major groove is slightly deeper than the minor groove (8.5 versus 7.5 Angstroms). The grooves have different widths because of the asymmetric attachment of the base pairs to the sugar-phosphate backbone. As a result the edges of the base pairs in the major groove are wider than those in the minor groove. Each groove is lined by potential hydrogen-bond donor and acceptor atoms, and these interact with DNA-binding proteins that recognize specific DNA sequences. For example, endonucleases bind electrostatically to the minor groove of the double-helical DNA. The figure below shows the binding of a helix-turn-helix motif (q.v.) to a DNA segment. The minor groove, the major groove, and the recognition helix are labeled G m, G M, and RH, respectively. See Antennapedia, deoxyribonuclease.
Subjects: Genetics and Genomics.