ICMT, also named as PCCMT and PPMT, belongs to the isoprenylcysteine O-methyltransferase family. ICMT is the third of three enzymes that posttranslationally modify isoprenylated C-terminal cysteine residues in certain proteins and target those proteins to the cell membrane. It localizes to the endoplasmic reticulum. Alternative splicing may result in other transcript variants, but the biological validity of those transcripts has not been determined. It is ubiquitously expressed. It expressed at higher levels in the cerebellum and putamen than in other brain regions and abundant expression seen in the Purkinje cells and pontine neurons.