Table 3.

Some posttranslational chemical modifications of proteins that affect protein migration in SDS-PAGE

Modification	Modified	Modification	Modified (kDa)
Ubiquitination	[8.56]1-n (n ≥ 20)	Heme C	0.62
SUMOylation	[12]1-n a (n ≥ 10)	Flavin (FMN/FAD)	0.46/0.79
FATylation	[18]1-n (n ≥ 3)	Phosphopantetheine	0.34
NEDDylation	[6,7,8,9,10]1-n (n ≥ 5)	Retinylidene	0.28
ISGylation	17a,b	Lipoylation	0.19
ADP-ribosylation	[0.54]1-n (n ≥ 200)	GPI (GPI-like) anchor	2-3
Adenylylation	0.33	Cholesterolation	0.4
Glycosylation	[0.13-0.31]3-n (n ≥ 30)	Geranylgeranylation	0.27
Glycation	0.16c	Palmitoylation	0.24
Polyglycylation	[0.06]1-n (n ≥ 40)	Farnesylation	0.21
Polyglutamylation	[0.13]1-n (n ≥ 6)	Myristoylation	0.19
S-Glutathionylation	0.31	Diphthamidation	0.30
Arginylation	0.16	ETA phosphoglycerylation	0.27
Iodination	0.13	Phosphoglycerylation	0.17
Succinylation	0.10	Phosphorylation	1-2

Note: Most of the modifications increase the molecular weight of the protein and thus decelerate migration of the protein in SDS-PAGE, but some, such as phosphorylation, may sometimes accelerate migration when they change electronic charge of the protein more significantly than the molecular weight. (a) Both of the modification moieties could form mixed chains with ubiquitin; (b) there have not been poly-ISG15 chains or enzymes reported so far that are involved in the formation of poly-ISG15 chains; and (c) the glycation products could be further modified to produce inter-protein cross-links, carboxymethyl lysines, and other intermediates. SUMO-, small ubiquitin-related modifier; FAT-, HLA-F adjacent transcript; NEDD-, neural precursor cell expressed, developmentally down-regulated; ISG-, interferon-stimulated gene; ADP, adenosine diphosphate; FMN, flavin mononucleotide; FAD, flavin adenine dinucleotide; GPI, glycosylphosphatidylinositol; and ETA, ethanolamine.