期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 103, 期 15, 页码 5752-5757出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0509723103
关键词
nonspecific binding; shear flow stretching; single-molecule imaging; DNA glycosylase mechanism; hopping
资金
- NCI NIH HHS [R01 CA100742, CA100742] Funding Source: Medline
- NIGMS NIH HHS [GM061577, R01 GM044853, ST32 GM07598-25, T32 GM007598] Funding Source: Medline
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 W). 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.
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