Poster: Intracellular Signaling

Abs # 842: Prenylcysteine a-carboxyl methylesterase in Arabidopsis thaliana

Presenter:	Crowell, Dring N, dcrowell@iupui.edu
Authors	Crowell, Dring N (A)   Bultema, Rebecca L (A)
Affiliations:	(A): Department of Biology, Indiana University-Purdue University Indianapolis

Prenylated proteins are modified by thioether linkage to a 15-carbon farnesyl or a 20-carbon geranylgeranyl moiety. For most prenylated proteins, this modification occurs at a cysteine residue located four amino acids from the carboxyl terminus. Subsequently, these proteins undergo proteolytic removal of the three amino acids at the carboxyl terminus and carboxyl methylation of the prenylcysteine residue. Two distinct prenylcysteine a-carboxyl methyltransferases, encoded by the AtSTE14A and AtSTE14B genes, catalyze carboxyl methylation of prenylated proteins in Arabidopsis thaliana. Consistent with the hypothesis that this is a reversible and potentially regulated step in the processing of prenylated plant proteins, we describe a specific prenylcysteine a-carboxyl methylesterase activity in Arabidopsis extracts. Furthermore, an exhaustive search of the Arabidopsis genome for genes encoding protein products with esterase signature motifs and isoprenoid binding sites revealed three candidate genes potentially encoding prenylcysteine a-carboxyl methylesterase activity. The significance of reversible methylation and demethylation of prenylated proteins in Arabidopsis will be discussed in the context of ABA signaling and meristem development.