198 Topics in Current Chemistry Editorial Board: A. de Meijere KN ...

50 J.P. Glusker
Fig. 39. Hydrogen-bonding patterns of base pairs [103]
are formed. Netropsin NH groups form hydrogen bonds to DNA, as shown in
Fig. 38, while ring hydrogen atoms are in contact with the CH groups (on C2) of
adenine. If there is an amino group in these positions (giving guanine instead of
adenine), netropsin could not bind. The specificity of netropsin for A◊ T base
pairs is determined by a combination of hydrogen bonding and van der Waals
interactions. Modification of the chemical formula of netropsin can provide a
G ◊ C-specific binding agent [100].
9.3
Protein-Nucleic Acid Interactions
Proteins can interact with nucleic acids by means of a helix-turn-helix motif
[101] in the protein structure, by a zinc finger [71, 72], or by a leucine zipper
[102] in which leucine side chains that are seven amino-acid residues apart on
along each of two a helices interact and force a protein conformation that is