2ae9

Solution Structure of the theta subunit of DNA polymerase III from E. coliSolution Structure of the theta subunit of DNA polymerase III from E. coli

Structural highlights 2ae9 is a 1 chain structure with sequence from Escherichia coli. Full experimental information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Solution NMR Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function HOLE_ECOLI DNA polymerase III is a complex, multichain enzyme responsible for most of the replicative synthesis in bacteria. This DNA polymerase also exhibits 3' to 5' exonuclease activity. The exact function of the theta subunit is unknown. 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 PubMed The catalytic core of Escherichia coli DNA polymerase III holoenzyme contains three subunits: alpha, epsilon, and theta. The alpha subunit contains the polymerase, and the epsilon subunit contains the exonucleolytic proofreading function. The small (8-kDa) theta subunit binds only to epsilon. Its function is not well understood, although it was shown to exert a small stabilizing effect on the epsilon proofreading function. In order to help elucidate its function, we undertook a determination of its solution structure. In aqueous solution, theta yielded poor-quality nuclear magnetic resonance spectra, presumably due to conformational exchange and/or protein aggregation. Based on our recently determined structure of the theta homolog from bacteriophage P1, named HOT, we constructed a homology model of theta. This model suggested that the unfavorable behavior of theta might arise from exposed hydrophobic residues, particularly toward the end of alpha-helix 3. In gel filtration studies, theta elutes later than expected, indicating that aggregation is potentially responsible for these problems. To address this issue, we recorded 1H-15N heteronuclear single quantum correlation (HSQC) spectra in water-alcohol mixed solvents and observed substantially improved dispersion and uniformity of peak intensities, facilitating a structural determination under these conditions. The structure of theta in 60/40 (vol/vol) water-methanol is similar to that of HOT but differs significantly from a previously reported theta structure. The new theta structure is expected to provide additional insight into its physiological role and its effect on the epsilon proofreading subunit. Nuclear magnetic resonance solution structure of the Escherichia coli DNA polymerase III theta subunit.,Mueller GA, Kirby TW, DeRose EF, Li D, Schaaper RM, London RE J Bacteriol. 2005 Oct;187(20):7081-9. PMID:16199579 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also DNA polymerase 3D structures

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