Biology Reference
In-Depth Information
218
However, with the addition of topo-isomerase I, the two bands collapse into
one. Furthermore, under that condition, digestion by restriction enzymes is
even more retarded. How are these biological macro-molecules interacting
with each other (see, for example, Arimondo
et al.
, 2000)?
Three Dimensional Folding of DNA
Since the discovery of DNA double helix more than 40 years ago, the three-
dimensional folding of DNA, or DNA tertiary structure, is largely unknown.
How is the DNA molecule packed inside the head of a lambda phage? On
osmotic shock, the phage DNA will exhibit many loops. Since the detailed
folding of this 50 kb DNA molecule is not understood, larger DNA
molecules are essentially beyond comprehension. Various basic proteins are
intimately associated with DNA, but the detailed protein-DNA interactions
are also not understood, except in a few cases. As discussed in the previous
chapter, the study of three-dimensional structures of DNA will be a major
endeavor in the future.
REFERENCES
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Arimondo PB, Riou J-F, Mergny J-L, Tazi J, Sun J-S, Garestier T and Helene C (2000)
Interaction of human DNA topoisomerase I with G-quartet structures.
Nucl. Acids Res.,
28
,
4832-4838.
Cochran W, Crick FHC and Vand V (1952) The structure of synthetic polypeptides. I. The
transforms of atoms on a helix.
Acta Cryst.,
5
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Franklin RE and Gosling RG (1953) Molecular configuration in sodium thymonucleate.
Nature,
171
, 740-741.
Gehring K, Leroy J-L and Gueron M (1993) A tetrameric DNA structure with protonated
cytosine-cytosine base pairs.
Nature,
363
, 561-565.
Langridge R, Wilson HR, Cooper CW, Wilkins MHF and Hamilton LD (1960) The
molecular configuration of deoxyribonucleic acid. I. X-ray diffraction study of crystalline
form of lithium salt.
J. Mol. Biol.,
2
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