Protein-S-isoprenylcysteine O-methyltransferase explained
| Symbol: | ICMT |
| ICMT |
| Pfam: | PF04140 |
| Pfam Clan: | CL0115 |
| Interpro: | IPR007269 |
| Opm Family: | 159 |
| Opm Protein: | 4a2n |
| protein-S-isoprenylcysteine O-methyltransferase |
| Ec Number: | 2.1.1.100 |
| Cas Number: | 130731-20-3 |
| Go Code: | 0004671 |
The isoprenylcysteine o-methyltransferase carries out carboxyl methylation of cleaved eukaryotic proteins that terminate in a CaaX motif. In Saccharomyces cerevisiae (Baker's yeast) this methylation is carried out by Ste14p, an integral endoplasmic reticulum membrane protein. Ste14p is the founding member of the isoprenylcysteine carboxyl methyltransferase (ICMT) family, whose members share significant sequence homology.[1]
The enzyme catalyzes the chemical reaction
S-adenosyl-L-methionine + protein C-terminal S-farnesyl-L-cysteine
S-adenosyl-L-homocysteine + protein C-terminal S-farnesyl-L-cysteine methyl ester
Thus, the two substrates of this enzyme are S-adenosyl methionine and protein C-terminal S-farnesyl-L-cysteine, whereas its two products are S-adenosylhomocysteine and protein C-terminal S-farnesyl-L-cysteine methyl ester.
References
- Clarke S, Vogel JP, Deschenes RJ, Stock J . 1988 . Posttranslational modification of the Ha-ras oncogene protein: evidence for a third class of protein carboxyl methyltransferases . Proc. Natl. Acad. Sci. U.S.A. . 85 . 4643 - 7 . 3290900 . 10.1073/pnas.85.13.4643 . 13 . 280491 . 1988PNAS...85.4643C . free .
- Ota IM, Clarke S . 1989 . Enzymatic methylation of 23-29-kDa bovine retinal rod outer segment membrane proteins. Evidence for methyl ester formation at carboxyl-terminal cysteinyl residues . J. Biol. Chem. . 264 . 12879 - 84 . 2753892 . 22 . 10.1016/S0021-9258(18)51569-6 . free .
- Stephenson RC, Clarke S . 1990 . Identification of a C-terminal protein carboxyl methyltransferase in rat liver membranes utilizing a synthetic farnesyl cysteine-containing peptide substrate . J. Biol. Chem. . 265 . 16248 - 54 . 2398053 . 27 . 10.1016/S0021-9258(17)46215-6 . free .
Notes and References
- Romano JD, Michaelis S . Topological and mutational analysis of Saccharomyces cerevisiae Ste14p, founding member of the isoprenylcysteine carboxyl methyltransferase family . Mol. Biol. Cell . 12 . 7 . 1957–71 . July 2001 . 11451995 . 55642 . 10.1091/mbc.12.7.1957.
