Below are the structures of
AZT (3'-azido-2',3'-dideoxythymidine), a nucleoside analog inhibitor of Reverse
Transcriptase, and dCTP, a normal building block of DNA. Note that the 3'
carbon of CTP has an attached oxygen, and
that in AZT this oxygen has been replaced with 2 nitrogens
of the azido group. Both molecules are deoxy at the 2' carbon. AZT is capable
of being incorporated into a DNA chain, but causes chain termination because there
is no 3' oxygen at the end of the growing chain to nucleophillically attack an
incoming nucleotide.
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