Table 1.

Averaged human lens PTM spectral counts and PTM rates (for peptides containing detected modifications) for aged water-insoluble and water-soluble crystallins.

		Average Aged Human Lens Spectral Counts (N=3)a,b					3-Day Old Spectral Countsc
		Overall	Water-Insoluble		Water-Soluble		Water-Soluble
Modification	aa, ΔM	Relative Rankd	Modified Count	Ratee (%)	Modified Count	Ratee (%)	Modified Count	Ratee (%)
deamidation	N,Q +1	93	1,739	18.52	796	8.77	176	2.30
S-methylation	C -43f	28	390	28.80	374	20.30	6	0.45
acetylationg	nt +42	24	300	84.89	355	83.78	420	80.15
oxidation	M,W +16	11	143	2.76	169	3.57	153	4.27
carboxymethyl lysine	K +58	8	99	4.19	107	3.95	0	0.00
phosphorylation	S,T +80	7	80	3.83	113	5.46	20	1.12
carbamylation	K +43	3	33	4.28	39	4.52	5	0.68
carboxyethyl lysine	K +72	2	33	2.71	33	2.84	1	0.12
R +55	R +55	2	34	3.01	25	2.60	0	0.00
H-methylation	H +14	2	33	5.01	21	3.33	0	0.00
S,H +28	S,H +28	1	14	0.69	14	0.72	14	1.00

^aAged lenses were 70-year normal, 70-year mild cataract, and 93-year moderate cataract.

^bOverall spectral counts for the 11 major in vivo human lens crystallin modifications at 155 PTM sites.

^cSimilar quantities for water-soluble protein from a 3-day old lens are shown as a control.

^dRelative to least abundant modification. Ranked by total modified spectral count.

^eModification rate was calculated as the number of spectra assigned to a given amino acid modification divided by total number of spectra that contained those amino acids.

^fNet methylation mass shift after cysteine +57 Da carbamidomethylation.

^gProtein co-translational N-terminal acetylation.