Cysteine modification decreases glycosylase activity of OGG1. Modifying the cysteines of OGG1 by varying concentration of A, NEM or B, IAEDANS results in the loss of glycosylase activity. No treatment control is shown in black, 0.1 mM in orange, 0.25 mM in blue, and 0.5 mM in red. IAEDANS, 5-({2-[(iodoacetyl)amino]ethyl}amino)naphthalene-1-sulfonic acid; NEM, N-ethylmaleimide.