The interaction of illimaquinone, a selective inhibitor of the RNase H activity, with the reverse transcriptases of human immunodeficiency and murine leukemia retroviruses

• Published in: The Journal of biological chemistry Vol. 268; no. 13; pp. 9323 - 9328
• Main Authors: Loya, S, Hizi, A
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 05-05-1993
• Subjects: AIDS/HIV; Cloning, Molecular; Escherichia coli; Escherichia coli - enzymology; Escherichia coli - genetics; Ethylmaleimide - pharmacology; HIV Reverse Transcriptase; HIV-1 - enzymology; HIV-2 - enzymology; human immunodeficiency virus; Kinetics; Moloney murine leukemia virus - enzymology; murine leukemia virus; Quinones - pharmacology; Recombinant Proteins - antagonists & inhibitors; Reverse Transcriptase Inhibitors; Ribonuclease H - antagonists & inhibitors; RNA-Directed DNA Polymerase
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)98353-5

Illimaquinone, a natural marine product, was shown by us to inhibit preferentially the ribonuclease H (RNase H) activity of
the reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1). We have also shown that illimaquinone inhibits
the RNase H activity of HIV-2 RT in addition to that of HIV-1 RT, murine leukemia virus RT, and Escherichia coli RNase H.
Chemical modifications of HIV-1 RT by sulfhydryl-specific reagents, such as N-ethylmaleimide (NEM) have been demonstrated
to specifically inhibit the RNase H activity of the enzyme. Since our previous studies have suggested that cysteine 280 in
HIV-1 RT interacts with the sulfhydryl reagents, we have examined the possibility that illimaquinone interacts with the RT
molecules via amino acid residues located in the vicinity of cysteine 280 in both HIV-1 and HIV-2 RTs. In the combined effect
studies of illimaquinone and NEM, the two structurally unrelated compounds were shown to be mutually exclusive, exhibiting
an antagonistic interaction with both HIV-1 and murine leukemia virus-associated RNase H activities. This implicates cysteine
280, in both HIV-1 and HIV-2 RTs, to be in close proximity to the putative binding site of the enzyme to illimaquinone. The
above conclusion is further supported by the fact that the RNase H activity of an enzymatically active mutant of HIV-1 RT,
in which cysteine 280 was replaced by serine, was substantially more resistant to illimaquinone than the corresponding activity
of the wild-type enzyme. The fact that NEM failed to inhibit E. coli RNase H as opposed to illimaquinone highlights a major
difference between the retroviral and bacterial RNase H.