Nucleic Acids Research, 2002, Vol. 30, No. 10 2097-2102
© 2002 Oxford University Press
A novel type of uracil-DNA glycosylase mediating repair of hydrolytic DNA damage in the extremely thermophilic eubacterium Thermus thermophilus
Abteilung Molekulare Genetik und Präparative Molekularbiologie and Göttingen Genomics Laboratory, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstraße 8, D-37077 Göttingen, Germany
Spontaneous hydrolytic deamination of DNA cytosine and 5-methyl-cytosine residues is an abundant source of C/G (5-meC/G) to T/A transition mutations. As a result of this pressure, at least six different families of enzymes have evolved that initiate repair at U/G (T/G) mispairs, the relevant pre-mutagenic intermediates. The necessarily higher rate of the process at elevated temperatures must pose a correspondingly accentuated problem to contemporary thermophilic organisms and may have been a serious bottleneck in early evolution when life passed through a phase of very high ambient temperatures. Here we show that Thermus thermophilus, an aerobic, Gram-negative eubacterium thriving at up to 85°C, harbors two uracil-DNA glycosylases (UDGs), termed TTUDGA and TTUDGB. According to both amino acid sequence and enzymatic properties, TTUDGA clearly belongs to the family of ‘thermostable UDGs’. TTUDGB shares with TTUDGA 23% sequence identity, but differs from it in profound functional aspects. TTUDGB, unlike TTUDGA, does not act upon uracil residues in the context of single-stranded DNA whereas both enzymes process various double-stranded substrates, albeit with different preferences. TTUDGB shows a number of sequence features characteristic of the UDG superfamily, but surprisingly lacks any polar residue within its so-called motif 1 (GLAPG-X10-F). This finding is in conflict with a previously assumed crucial catalytic role of motif 1 in water activation and supports a more recently suggested alternative of a dissociative (‘SN1-type’) reaction mechanism. Together, the characteristics of TTUDGB and its homologs in other organisms define a novel family of UDG repair enzymes.
* To whom correspondence should be addressed. Tel: +49 551 39 3801; Fax: +49 551 39 3805; Email: hfritz{at}uni-molgen.gwdg.dePresent address:Vytaute Starkuviene, European Molecular Biology Laboratory, Meyerhofstraße 1, D-69117 Heidelberg, Germany
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. Georg, L. Schomacher, J. P. J. Chong, A. I. Majernik, M. Raabe, H. Urlaub, S. Muller, E. Ciirdaeva, W. Kramer, and H.-J. Fritz The Methanothermobacter thermautotrophicus ExoIII homologue Mth212 is a DNA uridine endonuclease Nucleic Acids Res., October 6, 2006; 34(18): 5325 - 5336. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Castan, L. Casares, J. Barbe, and J. Berenguer Temperature-Dependent Hypermutational Phenotype in recA Mutants of Thermus thermophilus HB27 J. Bacteriol., August 15, 2003; 185(16): 4901 - 4907. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. H. Chung, E. K. Im, H.-Y. Park, J. H. Kwon, S. Lee, J. Oh, K.-C. Hwang, J. H. Lee, and Y. Jang A novel uracil-DNA glycosylase family related to the helix-hairpin-helix DNA glycosylase superfamily Nucleic Acids Res., April 15, 2003; 31(8): 2045 - 2055. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Laging, E. Lindner, H.-J. Fritz, and W. Kramer Repair of hydrolytic DNA deamination damage in thermophilic bacteria: cloning and characterization of a Vsr endonuclease homolog from Bacillus stearothermophilus Nucleic Acids Res., April 1, 2003; 31(7): 1913 - 1920. [Abstract] [Full Text] [PDF]
|
|