The Role of Prenylcysteine Methylation and Metabolism in Abscisic Acid Signaling in Arabidopsis thaliana

Abstract

Protein prenylation is a posttranslational modification resulting in thioether linkage of a 15-carbon farnesyl, or 20-carbon geranylgeranyl, moiety to a cysteine residue at or near the carboxyl terminus of a protein. Most prenylated proteins are further modified by carboxyl terminal proteolysis and/or methylation, the latter being the only reversible step in this series of modifications. In Arabidopsis thaliana, protein prenylation has been shown to be necessary for negative regulation of abscisic acid (ABA) signaling. This chapter summarizes recent literature on the role of methylation and demethylation of prenylated proteins in negative regulation of ABA signaling. Degradation of prenylated proteins generates farnesylcysteine (FC) and geranylgeranylcysteine (GGC), which are potent competitive inhibitors of isoprenylcysteine methyltransferase (ICMT), the enzyme that methylates the carboxyl terminus of prenylated proteins. Thus, FC and GGC metabolism also affects ABA signaling, and this chapter summarizes recent literature on prenylcysteine metabolism and its role in negative regulation of ABA signaling.