Conformational stability of dimeric HIV-1 and HIV-2 reverse transcriptases

被引:36
作者
Divita, G
Rittinger, K
Restle, T
Immendorfer, U
Goody, RS
机构
[1] MAX PLANCK INST MOLEK PHYSIOL, PHYS BIOCHEM ABT, D-44026 DORTMUND, GERMANY
[2] MAX PLANCK INST MED RES, BIOPHYS ABT, D-69120 HEIDELBERG, GERMANY
[3] YALE UNIV, DEPT MOLEC BIOPHYS & BIOCHEM, NEW HAVEN, CT 06511 USA
关键词
D O I
10.1021/bi00050a014
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The dissociation of dimeric reverse transcriptase (RT) of the human immunodeficiency virus (HIV) types 1 and 2 has been investigated using acetonitrile as a dissociating agent. The equilibrium transitions were monitored by combining different approaches (fluorescence spectroscopy, polymerase activity assay, and size-exclusion HPLC). The dissociation of RT induced a complete loss of polymerase activity and a 25% increase of the intrinsic fluorescence. It is fully reversible, and the midpoints of the equilibrium transition curves are dependent on the concentration of the enzyme used, suggesting a two-state transition model for the dissociation of RT in which dimers are in equilibrium with folded monomers. For both RTs, the heterodimeric form is more stable against dissociating agents and different pH than the corresponding homodimeric form. Moreover, heterodimeric HIV-2 RT exibits a higher stability than HIV-1 RT, with a free energy of dissociation of 12.1 kcal/mol at pH 6.5 and 25 degrees C, instead of 10 kcal/mol for HIV-1 RT. The binding of a primer/template induces a marked conformational change in both RTs, shown by the lower accessibility of the tryptophans to quenchers and the increase in tryptophan heterogeneity, and stabilized the dimeric form of both RTs (10-100-fold). The central role of hydrophobic interactions in dimer formation has been revealed by the 30% increase of exposure of the tryptophan cluster to quenchers upon dissociation of RT and the binding of 4 equiv of 1-anilino-8-naphthalenesulfonate to the dissociated enzymes.
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页码:16337 / 16346
页数:10
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