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| [[Image:2j6s.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_2j6s| PDB=2j6s | SCENE= }} | | {{STRUCTURE_2j6s| PDB=2j6s | SCENE= }} |
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| '''TERNARY COMPLEX OF SULFOLOBUS SOLFATARICUS DPO4 DNA POLYMERASE, O6-METHYLGUANINE MODIFIED DNA, AND DATP.'''
| | ===TERNARY COMPLEX OF SULFOLOBUS SOLFATARICUS DPO4 DNA POLYMERASE, O6-METHYLGUANINE MODIFIED DNA, AND DATP.=== |
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| ==Overview==
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| We examined the effect of a single O6-methylguanine (O6-MeG) template residue on catalysis by a model Y family polymerase, Dpo4 from Sulfolobus solfataricus. Mass spectral analysis of Dpo4-catalyzed extension products revealed that the enzyme accurately bypasses O6-MeG, with C being the major product (approximately 70%) and T or A being the minor species (approximately 20% or approximately 10%, respectively), consistent with steady-state kinetic parameters. Transient-state kinetic experiments revealed that kpol, the maximum forward rate constant describing polymerization, for dCTP incorporation opposite O6-MeG was approximately 6-fold slower than observed for unmodified G, and no measurable product was observed for dTTP incorporation in the pre-steady state. The lack of any structural information regarding how O6-MeG paired in a polymerase active site led us to perform x-ray crystallographic studies, which show that "wobble" pairing occurs between C and O6-MeG. A structure containing T opposite O6-MeG was solved, but much of the ribose and pyrimidine base density was disordered, in accordance with a much higher Km,dTTP that drives the difference in efficiency between C and T incorporation. The more stabilized C:O6-MeG pairing reinforces the importance of hydrogen bonding with respect to nucleotide selection within a geometrically tolerant polymerase active site.
| | The line below this paragraph, {{ABSTRACT_PUBMED_17105728}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 17105728 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_17105728}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Transferase/dna complex]] | | [[Category: Transferase/dna complex]] |
| [[Category: Translesion dna synthesis]] | | [[Category: Translesion dna synthesis]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 08:25:43 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 03:09:38 2008'' |
