Reverse transcriptase: Difference between revisions
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As a RNA-dependent DNA Polymerase, is able to recognize the initial RNA, transcribe it to ssDNA, cleave the remaining RNA and then build up the dsDNA, to do this the protein has two active catalytic zones. Chain A has the <scene name='Reverse_transcriptase/Fingers/1'>Polymerase active site</scene> that consist of two ''finger-like'' domains, one of them recognizes the initial nucleic acid possibly by h-bonds interactions with phosphate groups of the side chains, then both domains make a conformational change closing the recognition hole to allow the second domain begin the transcription process; this change is allowed by a <scene name='Reverse_transcriptase/Flexible/1'>flexible zone</scene> between the two previous domains that is used as a common pharmaceutical target site in order to prevent this change and by this way inhibit the activity, but this one is the only zone of the Chain A that has non-conserved aminoacids giving the virus more drug resistance. | As a RNA-dependent DNA Polymerase, is able to recognize the initial RNA, transcribe it to ssDNA, cleave the remaining RNA and then build up the dsDNA, to do this the protein has two active catalytic zones. Chain A has the <scene name='Reverse_transcriptase/Fingers/1'>Polymerase active site</scene> that consist of two ''finger-like'' domains, one of them recognizes the initial nucleic acid possibly by h-bonds interactions with phosphate groups of the side chains, then both domains make a conformational change closing the recognition hole to allow the second domain begin the transcription process; this change is allowed by a <scene name='Reverse_transcriptase/Flexible/1'>flexible zone</scene> between the two previous domains that is used as a common pharmaceutical target site in order to prevent this change and by this way inhibit the activity, but this one is the only zone of the Chain A that has non-conserved aminoacids giving the virus more drug resistance. | ||
As the same rate that the polymerization process occurs, the other active site known as the <scene name='Reverse_transcriptase/Rnase/1'>Ribonuclease H domain</scene>, cleaves the RNA releasing the ssDNA that comes again trough the Polymerase active site to become dsDNA. Finally <scene name='Reverse_transcriptase/Chainb/1'>Chain B</scene> posibly has the function to stabilize the communication between the two active sites varying the length between them in order to synchronize both functions [http://www.biochem.ucl.ac.uk/bsm/xtal/teach/repl/rt.html] | As the same rate that the polymerization process occurs, the other active site known as the <scene name='Reverse_transcriptase/Rnase/1'>Ribonuclease H domain</scene>, cleaves the RNA releasing the ssDNA that comes again trough the Polymerase active site to become dsDNA. Finally <scene name='Reverse_transcriptase/Chainb/1'>Chain B</scene> posibly has the function to stabilize the communication between the two active sites varying the length between them in order to synchronize both functions [http://www.biochem.ucl.ac.uk/bsm/xtal/teach/repl/rt.html] | ||
This | This seems to be the most general idea of the mechanism of action of Reverse Transcriptase, however the process remains unclear and new approaches are being reported. [http://www.nature.com/nature/journal/v453/n7192/full/nature06941.html] | ||
One of the principal issues about this protein comparative with the usual DNA polymerase, is lack of a correction mechanism (usually made by DNA PolIII in the DNA Pol) that increase the quota of errors, producing more mutations and by this way giving more facultative and resistance abilities to the virus. | One of the principal issues about this protein comparative with the usual DNA polymerase, is lack of a correction mechanism (usually made by DNA PolIII in the DNA Pol) that increase the quota of errors, producing more mutations and by this way giving more facultative and resistance abilities to the virus. | ||
Revision as of 06:53, 30 November 2009
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Being the protein that gives their name to Retroviruses, Reverse Transcriptase is, in company of Protease and Integrase, the most important part of the protein system involved in the process of infection of viruses like HIV, MuLV and AMV, and has the unusual property of transcribing ssRNA into dsDNA going against the Central Dogma of Molecular Biology. Since its discovery in 1970, the study of its properties and mechanisms of action have been of high interest among the scientific community due to the unique properties that makes it an important medical target enzyme and important tool for genetic engineering applications like RT-PCR in the construction of cDNA libraries.
StructureStructure
This hand-like protein that has an usual length of 1000 residues(560 in Chain A and 440 for B), the third of them involved in alpha helical and almost a quarter in beta sheets, showing α+β domains; chain A with an usual weight of 65KDa contains the two actives sites and has the most conserved aminoacids, whereas chain B is around 50KDa and has more variable areas, result of drug resistant and function related evolution. [1]
FunctionFunction
As a RNA-dependent DNA Polymerase, is able to recognize the initial RNA, transcribe it to ssDNA, cleave the remaining RNA and then build up the dsDNA, to do this the protein has two active catalytic zones. Chain A has the that consist of two finger-like domains, one of them recognizes the initial nucleic acid possibly by h-bonds interactions with phosphate groups of the side chains, then both domains make a conformational change closing the recognition hole to allow the second domain begin the transcription process; this change is allowed by a between the two previous domains that is used as a common pharmaceutical target site in order to prevent this change and by this way inhibit the activity, but this one is the only zone of the Chain A that has non-conserved aminoacids giving the virus more drug resistance. As the same rate that the polymerization process occurs, the other active site known as the , cleaves the RNA releasing the ssDNA that comes again trough the Polymerase active site to become dsDNA. Finally posibly has the function to stabilize the communication between the two active sites varying the length between them in order to synchronize both functions [2] This seems to be the most general idea of the mechanism of action of Reverse Transcriptase, however the process remains unclear and new approaches are being reported. [3]
One of the principal issues about this protein comparative with the usual DNA polymerase, is lack of a correction mechanism (usually made by DNA PolIII in the DNA Pol) that increase the quota of errors, producing more mutations and by this way giving more facultative and resistance abilities to the virus.
See AlsoSee Also
- Reverse Transcriptase at Wikipedia
- Molecule of the Month (09/2002) at RCSB PDB
- List of Reverse Transcriptase articles at Proteopedia and at RCSB PDB
ReferencesReferences
[1] Consurf Server Data Base. Evolutionary conservation profile for Reverse Transcriptase PDB file 1JLB
[2] University College London. DNA Replication Enzymes
[3] Abbondanzieri E.A. 'et al.'. Nature 453, 184-189 (8 May 2008) | doi:10.1038/nature06941