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From Proteopedia
Crystal structure of HIV-1 reverse transcriptase (RT) in complex with JANSSEN-R157208
Structural highlights
Function[POL_HV1B1] Gag-Pol polyprotein and Gag polyprotein may regulate their own translation, by the binding genomic RNA in the 5'-UTR. At low concentration, Gag-Pol and Gag would promote translation, whereas at high concentration, the polyproteins encapsidate genomic RNA and then shutt off translation (By similarity).[1] Matrix protein p17 has two main functions: in infected cell, it targets Gag and Gag-pol polyproteins to the plasma membrane via a multipartite membrane-binding signal, that includes its myristoylated N-terminus. The second function is to play a role in nuclear localization of the viral genome at the very start of cell infection. Matrix protein is the part of the pre-integration complex. It binds in the cytoplasm the human BAF protein which prevent autointegration of the viral genome, and might be included in virions at the ration of zero to 3 BAF dimer per virion. The myristoylation signal and the NLS thus exert conflicting influences its subcellular localization. The key regulation of these motifs might be phosphorylation of a portion of MA molecules on the C-terminal tyrosine at the time of virus maturation, by virion-associated cellular tyrosine kinase. Implicated in the release from host cell mediated by Vpu (By similarity).[2] Capsid protein p24 forms the conical core that encapsulates the genomic RNA-nucleocapsid complex in the virion. Most core are conical, with only 7% tubular. The core is constituted by capsid protein hexamer subunits. The core is disassembled soon after virion entry. Interaction with human PPIA/CYPA protects the virus from restriction by human TRIM5-alpha and from an unknown antiviral activity in human cells. This capsid restriction by TRIM5 is one of the factors which restricts HIV-1 to the human species (By similarity).[3] Nucleocapsid protein p7 encapsulates and protects viral dimeric unspliced (genomic) RNA. Binds these RNAs through its zinc fingers. Facilitates rearangement of nucleic acid secondary structure during retrotranscription of genomic RNA. This capability is referred to as nucleic acid chaperone activity (By similarity).[4] The aspartyl protease mediates proteolytic cleavages of Gag and Gag-Pol polyproteins during or shortly after the release of the virion from the plasma membrane. Cleavages take place as an ordered, step-wise cascade to yield mature proteins. This process is called maturation. Displays maximal activity during the budding process just prior to particle release from the cell. Also cleaves Nef and Vif, probably concomitantly with viral structural proteins on maturation of virus particles (By similarity).[5] Reverse transcriptase/ribonuclease H (RT) is a multifunctional enzyme that converts the viral RNA genome into dsDNA in the cytoplasm, shortly after virus entry into the cell. This enzyme displays a DNA polymerase activity that can copy either DNA or RNA templates, and a ribonuclease H (RNase H) activity that cleaves the RNA strand of RNA-DNA heteroduplexes in a partially processive 3' to 5' endonucleasic mode. Conversion of viral genomic RNA into dsDNA requires many steps. A tRNA(3)-Lys binds to the primer-binding site (PBS) situated at the 5'-end of the viral RNA. RT uses the 3' end of the tRNA primer to perform a short round of RNA-dependent minus-strand DNA synthesis. The reading proceeds through the U5 region and ends after the repeated (R) region which is present at both ends of viral RNA. The portion of the RNA-DNA heteroduplex is digested by the RNase H, resulting in a ssDNA product attached to the tRNA primer. This ssDNA/tRNA hybridizes with the identical R region situated at the 3' end of viral RNA. This template exchange, known as minus-strand DNA strong stop transfer, can be either intra- or intermolecular. RT uses the 3' end of this newly synthesized short ssDNA to perform the RNA-dependent minus-strand DNA synthesis of the whole template. RNase H digests the RNA template except for two polypurine tracts (PPTs) situated at the 5'-end and near the center of the genome. It is not clear if both polymerase and RNase H activities are simultaneous. RNase H probably can proceed both in a polymerase-dependent (RNA cut into small fragments by the same RT performing DNA synthesis) and a polymerase-independent mode (cleavage of remaining RNA fragments by free RTs). Secondly, RT performs DNA-directed plus-strand DNA synthesis using the PPTs that have not been removed by RNase H as primers. PPTs and tRNA primers are then removed by RNase H. The 3' and 5' ssDNA PBS regions hybridize to form a circular dsDNA intermediate. Strand displacement synthesis by RT to the PBS and PPT ends produces a blunt ended, linear dsDNA copy of the viral genome that includes long terminal repeats (LTRs) at both ends (By similarity).[6] Integrase catalyzes viral DNA integration into the host chromosome, by performing a series of DNA cutting and joining reactions. This enzyme activity takes place after virion entry into a cell and reverse transcription of the RNA genome in dsDNA. The first step in the integration process is 3' processing. This step requires a complex comprising the viral genome, matrix protein, Vpr and integrase. This complex is called the pre-integration complex (PIC). The integrase protein removes 2 nucleotides from each 3' end of the viral DNA, leaving recessed CA OH's at the 3' ends. In the second step, the PIC enters cell nucleus. This process is mediated through integrase and Vpr proteins, and allows the virus to infect a non dividing cell. This ability to enter the nucleus is specific of lentiviruses, other retroviruses cannot and rely on cell division to access cell chromosomes. In the third step, termed strand transfer, the integrase protein joins the previously processed 3' ends to the 5' ends of strands of target cellular DNA at the site of integration. The 5'-ends are produced by integrase-catalyzed staggered cuts, 5 bp apart. A Y-shaped, gapped, recombination intermediate results, with the 5'-ends of the viral DNA strands and the 3' ends of target DNA strands remaining unjoined, flanking a gap of 5 bp. The last step is viral DNA integration into host chromosome. This involves host DNA repair synthesis in which the 5 bp gaps between the unjoined strands are filled in and then ligated. Since this process occurs at both cuts flanking the HIV genome, a 5 bp duplication of host DNA is produced at the ends of HIV-1 integration. Alternatively, Integrase may catalyze the excision of viral DNA just after strand transfer, this is termed disintegration (By similarity).[7] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedIn the treatment of AIDS, the efficacy of all drugs, including non-nucleoside inhibitors (NNRTIs) of HIV-1 reverse transcriptase (RT), has been limited by the rapid appearance of drug-resistant viruses. Lys103Asn, Tyr181Cys, and Tyr188Leu are some of the most common RT mutations that cause resistance to NNRTIs in the clinic. We report X-ray crystal structures for RT complexed with three different pyridinone derivatives, R157208, R165481, and R221239, at 2.95, 2.9, and 2.43 A resolution, respectively. All three ligands exhibit nanomolar or subnanomolar inhibitory activity against wild-type RT, but varying activities against drug-resistant mutants. R165481 and R221239 differ from most NNRTIs in that binding does not involve significant contacts with Tyr181. These compounds strongly inhibit wild-type HIV-1 RT and drug-resistant variants, including Tyr181Cys and Lys103Asn RT. These properties result in part from an iodine atom on the pyridinone ring of both inhibitors that interacts with the main-chain carbonyl oxygen of Tyr188. An acrylonitrile substituent on R165481 substantially improves the activity of the compound against wild-type RT (and several mutants) and provides a way to generate novel inhibitors that could interact with conserved elements of HIV-1 RT at the polymerase catalytic site. In R221239, there is a flexible linker to a furan ring that permits interactions with Val106, Phe227, and Pro236. These contacts appear to enhance the inhibitory activity of R221239 against the HIV-1 strains that carry the Val106Ala, Tyr188Leu, and Phe227Cys mutations. Crystal structures for HIV-1 reverse transcriptase in complexes with three pyridinone derivatives: a new class of non-nucleoside inhibitors effective against a broad range of drug-resistant strains.,Himmel DM, Das K, Clark AD Jr, Hughes SH, Benjahad A, Oumouch S, Guillemont J, Coupa S, Poncelet A, Csoka I, Meyer C, Andries K, Nguyen CH, Grierson DS, Arnold E J Med Chem. 2005 Dec 1;48(24):7582-91. PMID:16302798[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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