TABLE 1.

Summary of MALDI-TOF analysis of biotinylated XPA peptides

Presented are tryptic digest fragments containing biotinylated lysine residues. Lysine residues protected from modification in the presence of ATR are indicated by a +, whereas residues not protected by ATR are indicated by a −. The asterisk indicates that the biotinylated fragment is located in the His tag. The intensity of the biotinylated peptide peak 184–189 (Lys-188 + biotin) was at least 10-fold higher for free XPA treated with NHS-biotin than for XPA-ATR complex modified under identical conditions. Intensities of other biotinylated XPA peptide fragments in the absence and presence of ATR varied within ±20%.

Fragment	Modified Lys	Protection
(−18)–(−5)*	−12*	−
31–32	31	−
87–110	89	−
136–141	137	−
152–158	157	−
164–168	167	−
184–189	188	+
190–207	204	−
218–221	218	−
216–221	217, 218	−
219–224	221, 222	−
222–227	222, 224	−
223–227	224	−
232–237	236	−
259–273	259	−
260–273	272	−