Article

Multiple enzyme activities of Escherichia coli MutT protein for sanitization of DNA and RNA precursor pools.

Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Fukuoka 814-0193, Japan.
Biochemistry (impact factor: 3.42). 06/2005; 44(17):6670-4. DOI:10.1021/bi047550k pp.6670-4
Source: PubMed

ABSTRACT 8-OxoGua (8-oxo-7,8-dihydroguanine) is produced in nucleic acids as well as in nucleotide pools of cells, by reactive oxygen species normally formed during cellular metabolic processes. MutT protein of Escherichia coli specifically degrades 8-oxoGua-containing deoxyribo- and ribonucleoside triphosphates to corresponding nucleoside monophosphates, thereby preventing misincorporation of 8-oxoGua into DNA and RNA, which would cause mutation and phenotypic suppression, respectively. Here, we report that the MutT protein has additional activities for cleaning up the nucleotide pools to ensure accurate DNA replication and transcription. It hydrolyzes 8-oxo-dGDP to 8-oxo-dGMP with a K(m) of 0.058 microM, a value considerably lower than that for its normal counterpart, dGDP (170 microM). Furthermore, the MutT possesses an activity to degrade 8-oxo-GDP to the related nucleoside monophosphate, with a K(m) value 8000 times lower than that for GDP. These multiple enzyme activities of the MutT protein would facilitate the high fidelity of DNA and RNA syntheses.

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Keywords

8-OxoGua
 
accurate DNA replication
 
cellular metabolic processes
 
corresponding nucleoside monophosphates
 
degrade 8-oxo-GDP
 
dGDP
 
Escherichia coli
 
GDP
 
misincorporation
 
multiple enzyme activities
 
MutT possesses
 
MutT protein
 
normal counterpart
 
nucleic acids
 
nucleotide pools
 
reactive oxygen species
 
related nucleoside monophosphate
 
ribonucleoside triphosphates
 

Riyoko Ito