Figure 4

The OLD3 gene encodes the cytosolic OAS-TL. a) The old3-1 genomic region was cloned and transformed into Ler-0 wild type plants. A 14-day-old wild type Ler-0 plant and a representative Ler-0 plant carrying the old3-1 transgene are shown. b) Amino acid sequence alignment of the area surrounding G¹⁶² of three Arabidopsis OAS-TL proteins. The position of the G¹⁶² to E¹⁶² substitution in the cytosolic OAS-TL is indicated. Amino acids shown in green boxes are highly conserved amino acids; amino acid residues shown in red boxes are involved in the interaction with pyridoxal 5'-phosphate (PLP). The schematic drawing indicates the location of amino acids in helix-5 and helix-6. P (AT2G43750 - plastid OAS-TL); M (AT2G59760 - mitochondrial OAS-TL); C (AT4G14880 - OAS-A1). c) The location of PLP, Lys⁴⁶, which is the only residue forming a covalent bond (the Schiff base) with cofactor PLP, and His¹⁵⁷ that is involved in interacting with PLP are shown by stick drawings (highlighted black on orange). The position of Gly¹⁶² (gold) in helix-5 is shown as a CPK model. This residue is in close proximity with residues in helix-6 including Ala¹⁸⁹ (green), Tyr¹⁹² (white), and Leu¹⁹³ (purple). Figure made using Pymol, http://www.pymol.org/.