Skip to main content
. Author manuscript; available in PMC: 2010 Nov 16.
Published in final edited form as: Viruses. 2010 Jul 1;2(7):1476–1503. doi: 10.3390/v2071476

Figure 1.

Figure 1

Mechanisms of NRTI resistance. (A) Nucleotide excision. Mutations in pol, such as TAMs, aid in the ATP-mediated removal of an incorporated AZT monophosphate (AZT-MP) yielding an AZTppppA excision byproduct. (B) Nucleotide discrimination. Mutations in pol cause steric hindrance at the pol active site, excluding certain drugs, for example 3TC, from being incorporated during reverse transcription. Both examples yield a complex competent for polymerization. Yellow circle with the letter A and three phosphates, ATP; black circles with three phosphates, dNTPs; red circle with the letter Z and the N3 azido group, AZT-MP; blue circle with three phosphates, 3TC-triphosphate; P, phosphategroup. RNA is depicted with white circles; DNA is depicted with black circles.