Truncating alpha-helix E' of p66 human immunodeficiency virus reverse transcriptase modulates RNase H function and impairs DNA strand transfer

J Biol Chem. 1995 Mar 31;270(13):7068-76. doi: 10.1074/jbc.270.13.7068.


The properties of recombinant p66/p51 human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) containing C-terminal truncations in its p66 polypeptide were evaluated. Deletion end points partly or completely removed alpha-helix E' of the RNase H domain (p66 delta 8/p51 and p66 delta 16/p51, respectively), while mutant p66 delta 23/p51 lacked alpha E' and the beta 5'-alpha E' connecting loop. Although dimerization and DNA polymerase properties of all mutants were not significantly different from those of the parental enzyme, p66 delta 16/p51 and p66 delta 23/p51 RT lacked ribonuclease H (RNase H) activity. In contrast, RT mutant p66 delta 8/p51 retained endonuclease activity but lacked the directional processing feature of the parental enzyme. Despite retaining full endoribonuclease function, p66 delta 8/p51 RT barely supported transfer of nascent (-)-strand DNA between RNA templates representing the 5' and 3' ends of retroviral genome, shedding light on the requirement for the endonuclease and directional processing functions of the RNase H domain during replication.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • DNA Primers
  • DNA Replication*
  • DNA-Directed DNA Polymerase / metabolism
  • HIV Reverse Transcriptase
  • HIV-1 / enzymology*
  • Kinetics
  • Molecular Sequence Data
  • Mutagenesis
  • Nucleic Acid Conformation
  • Protein Structure, Secondary
  • RNA-Directed DNA Polymerase / biosynthesis
  • RNA-Directed DNA Polymerase / chemistry
  • RNA-Directed DNA Polymerase / metabolism*
  • Ribonuclease H / biosynthesis
  • Ribonuclease H / chemistry
  • Ribonuclease H / metabolism*
  • Sequence Deletion*
  • Templates, Genetic


  • DNA Primers
  • HIV Reverse Transcriptase
  • RNA-Directed DNA Polymerase
  • DNA-Directed DNA Polymerase
  • Ribonuclease H