5'-Methylthioadenosine Nucleosidase from Yellow Lupine (Lupinus luteus): Molecular Characterization and Mutational Analysis

Ewa      Bretes; Andrzej      Guranowski; Katarzyna      Nuc

Abstract

This is report of mutational analysis of higher plant 5'-methylthioadenosine nucleosidase (MTAN). We identified and characterized the gene encoding yellow lupine (Lupinus luteus) MTAN (LlMTAN). The role of active site amino acids residues Glu24, Phe134, Glu188 and Asp211 was analyzed by site-directed mutagenesis. The Glu24Gln and Asp211Asn substitutions completely abolished the enzyme activity. The Glu188Gln mutant showed only trace activity toward 5'-methylthioadenosine. These results indicate that these three amino acid residues are necessary for enzyme activity. Furthermore, as the result of replacement of Phe134 by less bulky leucine, LlMTAN acquired the ability to bind and hydrolyze S-adenosylhomocysteine. We also analyzed the sequence of the LlMTAN promoter region. It appeared that there may be a direct link between LlMTAN expression regulation and sulfate metabolism.

Keywords: 5'-Methylthioadenosine, 5'-Methylthioadenosine nucleosidase, Site-directed mutagenesis, Lupinus luteus, TALON resin, LlMTAN, gene encoding, clones, Plant Cis-acting Regulatory DNA Elements, gene expression, His-Mag agarose beads, lupine, variants, analogous, exons, MTA cycle, sulfur-compounds5'-Methylthioadenosine, 5'-Methylthioadenosine nucleosidase, Site-directed mutagenesis, Lupinus luteus, TALON resin, LlMTAN, gene encoding, clones, Plant Cis-acting Regulatory DNA Elements, gene expression, His-Mag agarose beads, lupine, variants, analogous, exons, MTA cycle, sulfur-compounds