. Author manuscript; available in PMC: 2006 Jul 1.

Published in final edited form as: Mol Endocrinol. 2006 Feb 23;20(7):1479–1493. doi: 10.1210/me.2005-0531

Table 1.

Quantitative mass spectrometric analysis of ERα reveals Lys268 as a major site of acetylation by p300.

Percentage of the total amount of ERα Tryptic Peptide Acetylated by p300 in an Acetyl CoA-dependent Manner¹
ERα Peptide (Lysines)	Total Acetylation	Single Acetylation²	Double Acetylation²	Major Site of Single Acetylation²
244-256 (K244, K252)	11.1 ± 0.7 %	10.4 ± 0.9 % (∼10.1% from K252, ∼0.3% from K244)	0.7 ± 0.4 %	K252 (∼97%)
264-269 (K266, K268)	31.5 ± 0.9 %	24.7 ± 0.9 % (∼23.5% from K268, ∼1.2% from K266)	6.8 ± 0.9 %	K268 (∼95%)
288-300 (K299)	4.5 ± 0.6 %	4.5 ± 0.6 %	N/A	K299 (100%)

Full-length ERα was acetylated by p300 in the presence of SRC(RID/PID) and E2. The acetylated ERα was then digested with trypsin and subjected to quantitative mass spectrometry as described in Materials and Methods. The percentage of the indicated peptide that was acetylated in an acetyl CoA-dependent manner was determined by comparing the results from acetylation reactions run with and without added acetyl CoA. Note that only the three peptides listed showed appreciable acetyl CoA-dependent acetylation by p300 in the mass spectrometry analysis. The values represent the mean ± SEM for three separate determinations.

As determined by MS/MS analysis using MALDI-ion trap mass spectrometry. The numbers in parentheses indicate the percentage of the singly acetylated peptide that was acetylated at the site listed.