Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
An abundant oxidative lesion, 8-oxo-7,8-dihydroguanine (8-oxoG), often directs the misincorporation of dAMP during replication. To prevent muta-tions, cells possess an enzymatic system for the removal of 8-oxoG. A key element of this system is 8-oxoguanine-DNA glycosylase (Fpg in bacteria, OGG1 in eukaryotes), which must excise 8-oxoG from 8-oxoG:C pairs but not from 8-oxoG:A. | ỊFEBS Journal Ionic strength and magnesium affect the specificity of Escherichia coli and human 8-oxoguanine-DNA glycosylases Viktoriya S. Sidorenko1 Grigory V. Mechetin1 Georgy A. Nevinsky1 2 and Dmitry O. Zharkov1 2 1 SB RAS Institute of ChemicalBiology and FundamentalMedicine Novosibirsk Russia 2 Department of NaturalSciences Novosibirsk State University Russia Keywords 8-oxoguanine DNA damage DNA glycosylase DNA repair substrate specificity Correspondence D. O. Zharkov SB RAS Institute of Chemical Biology and Fundamental Medicine Novosibirsk 630090 Russia Fax 7 383 333 3677 Tel 7 383 335 6226 E-mail dzharkov@niboch.nsc.ru Received 20 February 2008 revised 18 April2008 accepted 23 May 2008 doi 10.1111 j.1742-4658.2008.06521.x An abundant oxidative lesion 8-oxo-7 8-dihydroguanine 8-oxoG often directs the misincorporation of dAMP during replication. To prevent mutations cells possess an enzymatic system for the removal of 8-oxoG. A key element of this system is 8-oxoguanine-DNA glycosylase Fpg in bacteria OGG1 in eukaryotes which must excise 8-oxoG from 8-oxoG C pairs but not from 8-oxoG A. We investigated the influence of various factors including ionic strength the presence of Mg2 and organic anions polyamides crowding agents and two small heterocyclic compounds biotin and caffeine on the activity and opposite-base specificity of Escherichia coli Fpg and human OGG1. The activity of both enzymes towards 8-oxoG A decreased sharply with increasing salt and Mg2 concentration whereas the activity on 8-oxoG C was much more stable resulting in higher opposite-base specificity when salt and Mg2 were at near-physiological concentrations. This tendency was observed with both Cl and glutamate as the major anions in the reaction mixture. Kinetic and binding parameters for the processing of 8-oxoG C and 8-oxoG A by Fpg and OGG1 were determined under several different conditions. Polyamines crowding agents biotin and caffeine affected the activity and specificity of Fpg or .
