A base-excision DNA-repair protein finds intrahelical lesion bases by fast sliding in contact with DNA.
A central mystery in the function of site-specific DNA-binding proteins is the detailed mechanism for rapid location and binding of target sites in DNA. Human oxoguanine DNA glycosylase 1 (hOgg1), for example, must search out rare 8-oxoguanine lesions to prevent transversion mutations arising from oxidative stress. Here we report high-speed imaging of single hOgg1 enzyme molecules diffusing along DNA stretched by shear flow. Salt-concentration-dependent measurements reveal that such diffusion occurs as hOgg1 slides in persistent contact with DNA. At near-physiologic pH and salt concentration, hOgg1 has a subsecond DNA-binding time and slides with a diffusion constant as high as 5 x 10(6) bp(2)/s. Such a value approaches the theoretical upper limit for one-dimensional diffusion and indicates an activation barrier for sliding of only 0.5 kcal/mol (1 kcal = 4.2 kJ). This nearly barrierless Brownian sliding indicates that DNA glycosylases locate lesion bases by a massively redundant search in which the enzyme selectively binds 8-oxoguanine under kinetic control.
Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.
Paul C
PC
Blainey
Antoine M
AM
van Oijen
Anirban
A
Banerjee
Gregory L
GL
Verdine
X Sunney
XS
Xie
D019943:Amino Acid Substitution; D010582:Bacteriophage lambda / Q000235:genetics; D001665:Binding Sites; D004249:DNA Damage; D045647:DNA Glycosylases / Q000737:chemistry* / Q000378:metabolism*; D004260:DNA Repair; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics*; D006147:Guanine / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity
D004279:DNA, Viral; D011994:Recombinant Proteins; C024829:8-hydroxyguanine; D006147:Guanine; D045647:DNA Glycosylases; C479058:oxoguanine glycosylase 1, human