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Role of glutamine-151 of human immunodeficiency virus type-1 reverse transcriptase in RNA-directed DNA synthesis. 1997

N Kaushik, and D Harris, and N Rege, and M J Modak, and P N Yadav, and V N Pandey
Department of Biochemistry and Molecular Biology, UMD-New Jersey Medical School, Newark 07103, USA.

Glutamine-151 of HIV-1 RT has been shown to be a catalytically important residue through the characterization of its mutant phenotype Glu151Ala (Sarafianos et al., 1995a). To further understand the role of this residue, we have extended this analysis to include polymerization on natural RNA template in addition to DNA template. We find that Q151A mutant exhibited a severe reduction in the polymerase activity without any significant effect on the affinity for dNTP substrate. Unlike DNA-directed reactions, the rate-limiting step for RNA-directed reactions does not appear to be either at the dNTP binding step or the chemical step. Analysis of the products formed on natural heteromeric HIV-genomic RNA template annealed with an 18-mer DNA primer with a sequence complementary to the primer binding site (PBS) has shown that addition of nucleotides is nonlinear with time since the enzyme appears to stall on the RNA template following the incorporation of the first nucleotide. The Q151A mutant was found to be nearly devoid of pyrophosphorolytic activity on a RNA-PBS template-primer. Similar properties have been previously reported for a mutant of R72 (R72A) of HIV-1 RT (Sarafianos et al., 1995b). However, R72 was implicated in stabilizing the transition state ternary complex before and after the phosphodiester bond formation (Kaushik et al., 1996; Sarafianos et al., 1995b). Our results with Q151A suggest that the side chain of Q151 may help stabilize the side chain of R72, and the loss of pyrophosphorolysis activity observed with the Q151 mutant may be the indirect manifestation of this stabilizing effect on R72. These observations point to the functional interdependence of residues Q151 and R72 in the polymerase function of the enzyme. An analysis of the 3D model structure of HIV-1 RT bound to DNA-DNA and RNA-DNA template-primer reveals that the guanidine hydrogen of R72 seems to stabilize Q151 by hydrogen bonding with its amide oxygen. A systematic conformational search of the side chain of Q151 also suggests a stable orientation where its specific interaction with the base of the RNA template may aid in stabilizing it.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
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
D011487 Protein Conformation The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain). Conformation, Protein,Conformations, Protein,Protein Conformations
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
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
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
D001483 Base Sequence The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence. DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA
D001665 Binding Sites The parts of a macromolecule that directly participate in its specific combination with another molecule. Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D013698 Templates, Genetic Macromolecular molds for the synthesis of complementary macromolecules, as in DNA REPLICATION; GENETIC TRANSCRIPTION of DNA to RNA, and GENETIC TRANSLATION of RNA into POLYPEPTIDES. Genetic Template,Genetic Templates,Template, Genetic

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