I know there are PTMs that make use of the thiol group on cysteine, but does anyone know of any PTMs that add a thiol group to a protein (in any organism, not just humans)?
Oligosaccharides -- i.e., glycosyl groups -- can undergo thiolation. So if you are working with a N- or O-glycosylated protein, it is conceivable that you additoinally have a thioglyosylation event....