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The ribonuclease H activity of the reverse transcriptases of human immunodeficiency viruses type 1 and type 2 is modulated by residue 294 of the small subunit. 2003

Z Sevilya, and S Loya, and N Adir, and A Hizi
Department of Cell Biology and Histology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.

Reverse transcriptases (RTs) exhibit DNA polymerase and ribonuclease H (RNase H) activities. The RTs of human immunodeficiency viruses type 1 and type 2 (HIV-1 and HIV-2) are composed of two subunits, both sharing the same N-terminus (which encompasses the DNA polymerase domain). The smaller subunit lacks the C-terminal segment of the larger one, which contains the RNase H domain. The DNA polymerase domain of RTs resembles a right hand linked to the RNase H domain by a connection subdomain. Despite the high homology between HIV-1 and HIV-2 RTs, the RNase H activity of the latter is substantially lower than that of HIV-1 RT. The thumb subdomain of the small subunit controls the level of RNase H activity. We show here that Gln294, located in this thumb, is responsible for this difference in activity. A HIV-2 RT mutant, where Gln294 in the small subunit was replaced by a proline (present in HIV-1 RT), has an activity almost 10-fold higher than that of the wild-type RT. A comparative in vitro study of the kinetic parameters of the RNase H activity suggests that residue 294 affects the K(m) rather than the kcat value, influencing the affinity for the RNA.DNA substrate.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D011993 Recombinant Fusion Proteins Recombinant proteins produced by the GENETIC TRANSLATION of fused genes formed by the combination of NUCLEIC ACID REGULATORY SEQUENCES of one or more genes with the protein coding sequences of one or more genes. Fusion Proteins, Recombinant,Recombinant Chimeric Protein,Recombinant Fusion Protein,Recombinant Hybrid Protein,Chimeric Proteins, Recombinant,Hybrid Proteins, Recombinant,Recombinant Chimeric Proteins,Recombinant Hybrid Proteins,Chimeric Protein, Recombinant,Fusion Protein, Recombinant,Hybrid Protein, Recombinant,Protein, Recombinant Chimeric,Protein, Recombinant Fusion,Protein, Recombinant Hybrid,Proteins, Recombinant Chimeric,Proteins, Recombinant Fusion,Proteins, Recombinant Hybrid
D004259 DNA-Directed DNA Polymerase DNA-dependent DNA polymerases found in bacteria, animal and plant cells. During the replication process, these enzymes catalyze the addition of deoxyribonucleotide residues to the end of a DNA strand in the presence of DNA as template-primer. They also possess exonuclease activity and therefore function in DNA repair. DNA Polymerase,DNA Polymerases,DNA-Dependent DNA Polymerases,DNA Polymerase N3,DNA Dependent DNA Polymerases,DNA Directed DNA Polymerase,DNA Polymerase, DNA-Directed,DNA Polymerases, DNA-Dependent,Polymerase N3, DNA,Polymerase, DNA,Polymerase, DNA-Directed DNA,Polymerases, DNA,Polymerases, DNA-Dependent DNA
D005973 Glutamine A non-essential amino acid present abundantly throughout the body and is involved in many metabolic processes. It is synthesized from GLUTAMIC ACID and AMMONIA. It is the principal carrier of NITROGEN in the body and is an important energy source for many cells. D-Glutamine,L-Glutamine,D Glutamine,L Glutamine
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D012194 RNA-Directed DNA Polymerase An enzyme that synthesizes DNA on an RNA template. It is encoded by the pol gene of retroviruses and by certain retrovirus-like elements. EC 2.7.7.49. DNA Polymerase, RNA-Directed,RNA-Dependent DNA Polymerase,Reverse Transcriptase,RNA Transcriptase,Revertase,DNA Polymerase, RNA Directed,DNA Polymerase, RNA-Dependent,RNA Dependent DNA Polymerase,RNA Directed DNA Polymerase
D015497 HIV-1 The type species of LENTIVIRUS and the etiologic agent of AIDS. It is characterized by its cytopathic effect and affinity for the T4-lymphocyte. Human immunodeficiency virus 1,HIV-I,Human Immunodeficiency Virus Type 1,Immunodeficiency Virus Type 1, Human
D015498 HIV-2 An HIV species related to HIV-1 but carrying different antigenic components and with differing nucleic acid composition. It shares serologic reactivity and sequence homology with the simian Lentivirus SIMIAN IMMUNODEFICIENCY VIRUS and infects only T4-lymphocytes expressing the CD4 phenotypic marker. HTLV-IV,Human T-Lymphotropic Virus Type IV,Human immunodeficiency virus 2,LAV-2,HIV-II,Human Immunodeficiency Virus Type 2,Human T Lymphotropic Virus Type IV,Immunodeficiency Virus Type 2, Human,SBL-6669

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