Basavapathruni Aravind, Bailey Christopher M, Anderson Karen S
Yale University School of Medicine, Department of Pharmacology, New Haven, Connecticut 06520-8066, USA.
J Biol Chem. 2004 Feb 20;279(8):6221-4. doi: 10.1074/jbc.C300523200. Epub 2004 Jan 13.
Combination therapies treating human immunodeficiency virus type 1 (HIV-1) infection delay the emergence of drug-resistant virus and exhibit synergistic inhibition. This synergy is observed within the two classes of inhibitors that target the essential viral reverse transcriptase (RT): the chain-terminating nucleoside analogs (NRTIs) and the allosteric nonnucleosides (NNRTIs) that bind in a pocket distinct from the active site. A general mechanism to define the molecular basis for synergy between these two classes remains to be elucidated. Previous mechanistic studies from our laboratory (Spence, R. A., Kati, W. M., Anderson, K. S., and Johnson, K. A. (1995) Science 267, 988-993) have shown that the natural deoxynucleoside triphosphate and the NNRTI can simultaneously bind to their respective sites. This work also suggests communication between the two sites, since the inhibition of RT by NNRTIs is manifested through a remote effect on the chemical step. This interplay between the two sites offers a plausible hypothesis for understanding synergy in which binding of NNRTIs modulates the chain termination by NRTIs. The present study supports this hypothesis by illustrating that the clinically approved NNRTIs, nevirapine and efavirenz, inhibit the ATP-mediated removal of AZTMP, d4TMP, ddCMP, (-)3TCMP, (-)FTCMP, and (+)3TCMP, thereby prolonging the effectiveness of chain termination. This inhibition is mediated through an effect on both the rate of the chemical step and binding of ATP, resulting in an overall decrease in efficiency of removal. This work substantiates communication between the two binding pockets, the sustained use of combination therapy to treat HIV infection, and a molecular basis for understanding synergy.
联合疗法治疗人类免疫缺陷病毒1型（HIV-1）感染可延缓耐药病毒的出现并表现出协同抑制作用。在两类靶向关键病毒逆转录酶（RT）的抑制剂中观察到了这种协同作用：链终止核苷类似物（NRTIs）和在与活性位点不同的口袋中结合的变构非核苷（NNRTIs）。确定这两类抑制剂之间协同作用分子基础的一般机制仍有待阐明。我们实验室先前的机制研究（Spence, R. A., Kati, W. M., Anderson, K. S., and Johnson, K. A. (1995) Science 267, 988 - 993）表明，天然脱氧核苷三磷酸和NNRTI可以同时结合到它们各自的位点。这项工作还表明了两个位点之间的通信，因为NNRTIs对RT的抑制是通过对化学步骤的远程效应表现出来的。这两个位点之间的相互作用为理解协同作用提供了一个合理的假设，即NNRTIs的结合调节NRTIs的链终止。本研究通过说明临床批准的NNRTIs奈韦拉平和依非韦伦抑制ATP介导的AZTMP、d4TMP、ddCMP、(-)3TCMP、(-)FTCMP和(+)3TCMP的去除，从而延长链终止的有效性，支持了这一假设。这种抑制是通过对化学步骤的速率和ATP的结合的影响来介导的，导致去除效率总体下降。这项工作证实了两个结合口袋之间的通信、联合疗法治疗HIV感染的持续使用以及理解协同作用的分子基础。
