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Structural basis of HIV-1 resistance to AZT by excision

2010; Nature Portfolio; Volume: 17; Issue: 10 Linguagem: Inglês

10.1038/nsmb.1908

1545-9993

Xiongying Tu, Kalyan Das, Qianwei Han, Joseph D. Bauman, Arthur D. Clark, Xiaorong Hou, Yulia Volovik Frenkel, Barbara L. Gaffney, Roger A. Jones, Paul L. Boyer, Stephen H. Hughes, Stefan G. Sarafianos, Eddy Arnold,

Biochemical and Molecular Research

AZT is a nucleoside analog drug that inhibits HIV-1 reverse transcriptase (RT). The viral enzyme can acquire AZT resistance by mutations that enhance the rate of ATP-mediated excision of the incorporated AZT. Now structural work illustrates how the AZT resistance mutations create a high-affinity binding site for ATP and thus promote excision. Human immunodeficiency virus (HIV-1) develops resistance to 3′-azido-2′,3′-deoxythymidine (AZT, zidovudine) by acquiring mutations in reverse transcriptase that enhance the ATP-mediated excision of AZT monophosphate from the 3′ end of the primer. The excision reaction occurs at the dNTP-binding site, uses ATP as a pyrophosphate donor, unblocks the primer terminus and allows reverse transcriptase to continue viral DNA synthesis. The excision product is AZT adenosine dinucleoside tetraphosphate (AZTppppA). We determined five crystal structures: wild-type reverse transcriptase–double-stranded DNA (RT–dsDNA)–AZTppppA; AZT-resistant (AZTr; M41L D67N K70R T215Y K219Q) RT–dsDNA–AZTppppA; AZTr RT–dsDNA terminated with AZT at dNTP- and primer-binding sites; and AZTr apo reverse transcriptase. The AMP part of AZTppppA bound differently to wild-type and AZTr reverse transcriptases, whereas the AZT triphosphate part bound the two enzymes similarly. Thus, the resistance mutations create a high-affinity ATP-binding site. The structure of the site provides an opportunity to design inhibitors of AZT-monophosphate excision.