Speculation on the biological roles of left-handed Z-DNA
- Massachusetts Institute of Technology, Cambridge, MA (United States)
DNA is highly polymorphic and occurs largely as a right-handed double helix but can assume a remarkable variety of alternative conformations. DNA forms two distinct right-handed duplexes - A and B - the B form being the one most found in biological systems. An even more radical conformational change is associated with formation of the left-handed double helix, called Z-DNA. The relationship between these three different conformations can be considered in terms of energy. The ground state, or lowest energy level, is right-handed B-DNA. With a moderate amount of energy, the DNA can form the A conformation. With the input of a considerably greater amount of energy, the molecule can assume the left-handed Z conformation. Left-handed Z-DNA has been studied extensively. DNA was first crystallized and analyzed in a hexanucleotide that alternated in guanine and cytosine sequences. This sequence is highly favorable to Z-DNA formation, while alternating A-T sequences are less favorable. A number of conditions are found that stabilize Z-DNA in vitro. Two features are of primary significance for in vivo Z-DNA formation. The most important of these is negative supercoiling. The other important factor is associated with the presence of Z-DNA binding proteins. These proteins have the ability to stabilize the Z conformation, even in the absence of negative torsional strain.
- Research Organization:
- New York Academy of Sciences, New York, NY (United States)
- OSTI ID:
- 134835
- Report Number(s):
- CONF-9307221--
- Country of Publication:
- United States
- Language:
- English
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