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HIV-1 reverse transcriptase subunit interactions.
Lebowitz J; Braswell E; Kar S; McPherson S; Zhang CY; Richard D;
December 30, 1995
Natl Conf Hum Retroviruses Relat Infect (1st). 1993 Dec 12-16;:126.

Structural and biochemical evidence strongly supports a heterodimeric (p66p51) active form for HIV-1 reverse transcriptase (RT). Sedimentation studies were performed to extend the analysis of HIV-1 RT heterodimer stability. Heterodimer stability was examined as function of temperature and ionic strength. We have discovered that the association is only moderately stable at 5 and 20 degrees C. Model E sedimentation equilibrium experiments using NON-LIN regression software for data analysis gave heterodimer Kassoc values of 4.5-4.9x 10(5) and 2.5-2.9x 10(5) M-1 at 5 and 20 degrees C respectively. To our surprise, RT completely dissociates at 37 degrees C, and behaves as ideal monomeric species. The dissociation of RT as a function of increasing temperature was also observed by measuring the decrease in sedimentation velocity (sw,20) between 21 and 37 degrees C. If stabilization of the heterodimer was due primarily to hydrophobic interactions we would anticipate an increase in the association from 21 degrees C to 37 degrees C. The opposite temperature dependence for the association of RT suggests that electrostatic and hydrogen bond interactions are the important interactions that promote heterodimer stability. To examine the effect of ionic strength on p66p51 association we determined the changes in sw,20 as a function of NaCl concentration. There is a sharp decrease in sw,20 between 0.10 and 0.5M NaCl, leading to apparent complete dissociation. Temperature and salt induced dissociation was reversible. The above results suggest that the electrostatic interactions contribute significantly to heterodimer stability. The stability of the RT heterodimer must be increased substantially by the formation of an active RT-primer/template binary complex since 37 degrees C appears to induce complete dissociation of free RT. We believe that our preliminary data suggests the potential for interface peptide inhibitors capable of dissociating RT thereby inactivating the enzyme.

DNA Primers Electrochemistry Enzyme Stability HIV-1/*ENZYMOLOGY Osmolar Concentration Regression Analysis RNA-Directed DNA Polymerase/*CHEMISTRY/METABOLISM Temperature Templates ABSTRACT