Chapter eleven The SABATH family of MTS in Arabidopsis Thaliana and other plant species

SABATH MTs are found only in the plant kingdom, and they also do not display significant sequence similarity to other known plant MTs. However, they share several physical characteristics with some other families of plant MTs, such as forming homodimers and sharing similar SAM binding residues. The SABATH protein family appears to be unique among plant MT families in containing enzymes that transfer the methyl group to an oxygen while other members of the family transfer the methyl group to a nitrogen; previously described plant MT families contain members that appear to modify only one type of functionality. Although 24 SABATH gene family members have been found in Arabidopsis, the protein encoded by only one of them has been biochemically characterized. Further characterization of SABATH genes from Arabidopsis and other species of plants should help to provide a better understanding of the range and types of functional groups that this family of enzymes can modify by methylation. In addition, modeling of the active sites of Arabidopsis SABATH proteins with unknown function, using the crystal data of Clarkia breweri SAMT, may help in the identification of potential substrates, and may also assist in understanding the evolution of function in this gene family. The addition of sequence and linkgage data from other species such as Arabidopsis lyrata, Medicago truncatula, and Oryza sativa may also aid in our understanding of both the phylogenetic relationships among SABATH genes and their functions.