[28] THERMODYNAMIC ANALYSIS OF CAPRAVIRINE BINDING TO HIV REVERSE TRANSCRIPTASE AND INHIBITION OF DNA POLYMERASE AND RNASE H ACTIVITIES

13th International HIV Drug Resistance Workshop

8–12 June 2004, Tenerife Sur-Costa Adeje, Canary Islands, Spain

THERMODYNAMIC ANALYSIS OF CAPRAVIRINE BINDING TO HIV REVERSE TRANSCRIPTASE AND INHIBITION OF DNA POLYMERASE AND RNASE H ACTIVITIES

Antiviral Therapy 2004; 9:S34

S Rajendran, JQ Hang, Y Yang, Y Li, S Tsing, J Barnett, N Cammack, A Ahene and K Klumpp
Roche Palo Alto LLC, Palo Alto, Calif., USA

Structurally diverse non-nucleoside reverse transcriptase inhibitors (NNRTI) can bind to a defined NNRTI binding pocket on the polymerase domain of HIV reverse transcriptase (HIV-RT). At present, the relationship between HIV-RT binding affinity and inhibitory potency of NNRTIs is unclear. Capravirine (S-1153) was used as a prototype NNRTI to determine the thermodynamic parameters of the binding interaction with HIV-RT. Capravirine binding to HIV-RT was enthalpy driven at temperatures above 21°C and entropy driven at temperatures below 12°C. The binding was associated with potent inhibition of DNA polymerase activity and partial inhibition of polymerase independent RNase H activity through long-range inhibition at the RNase H domain. Binding affinity of capravirine to the HIV-RT Y181C point mutant protein was reduced six-fold and associated with a significant loss in binding enthalpy (4.4 kcal/mol), which was partly compensated by an entropy gain. Binding to the K103N point mutant protein was increased 2.4-fold as compared to wild-type. The double mutant K103N/Y181C showed an intermediate loss of binding enthalpy (3.5 kcal/mol), but a highly reduced binding affinity (16.4-fold), due to lower entropy compensation as compared to Y181C. The thermodynamic binding parameters for capravirine binding were consistent with different protein interactions in wild-type and mutant proteins. The inhibitory potency of capravirine on RNase H and polymerase activity was highest with wild-type protein and reduced with mutant proteins. However, there was no direct correlation between the effect of resistance mutations on protein binding, polymerase and RNase H inhibition. The molecular understanding of the relationship between NNRTI binding and enzyme inhibition will improve prediction of inhibitory potencies from in silico binding models.

PRESENTING AUTHOR: K Klumpp

Download PDF of this abstract.

2004-06-08
28

Copyright © 2004 - International Medical Press Ltd.. Reproduction of this abstract (other than one copy for personal reference) must be cleared through the International Medical Press Ltd. 2-4 Idol Lane, London EC3R 5DD UK.