DefinitionThis section has been translated automatically.
Supercoiling (from super- and coil = winding) refers to an additional spatial twisting of the helical double-stranded DNA.
General informationThis section has been translated automatically.
For example, the helical DNA in prokaryotic cell nuclei is twisted by enzymes (e.g. bacterial topoisomerases (gyrases) into simple "supercoils" tangled structures (double strand, deoxyribonucleic acids). They thus resemble a curled telephone cord. In a relaxed DNA, the two nucleotide strands wind around the helical axis approximately every 10.5 base pairs. Such a twist is called a "twist".
If these supercoils are twisted around themselves again, the DNA chains are tightly packed in the nucleus. Their space requirement decreases dramatically. Since the total length of the DNA of a cell is often a thousand times the diameter of the cell, supercoiling is essential for the functioning of prokaryotic and eukaryotic cells.
Depending on the direction in which supercoiling takes place, a distinction is made between:
- positive supercoiling (left-handed or counterclockwise) and
- negative supercoiling (right-handed or clockwise).
Topoisomerases are responsible for the enzymatic control of supercoiling.
