The recognition and removal of an altered base by a DNA glycosylase is thought to involve the diffusion of the enzyme along the minor grove of the DNA molecule. The enzyme presumably compresses the backbone of the affected DNA strand at the site of damage. This compression is thought to result in an outward rotation of the damaged residue into a "pocket" of the enzyme that recognizes and cleaves the altered base from the backbone (Slupphaug et al. 1996, Parikh et al. 1998).