title: A tomato alternative oxidase protein with altered regulatory properties.
abstract: We have investigated the expression and regulatory properties of the two alternative oxidase (Aox) proteins that are expressed in tomato (Lycopersicon esculentum L. Mill cv. Sweetie) after storage of green fruit at 4 degrees C. Four Aox genes were identified in the tomato genome, of which two (LeAox1a and LeAox1b) were demonstrated to be expressed in cold-treated fruit. The activity and regulatory properties of LeAox1a and LeAox1b were assayed after expression of each protein in yeast cells (Saccharomyces cerevisiae), proving that each is an active Aox protein. The LeAox1b protein was shown to have altered regulatory properties due to the substitution of a Ser for the highly conserved Cys(I) residue. LeAox1b could not form inactive disulfide-linked dimers and was activated by succinate instead of pyruvate. This is the first example of a dicot species expressing a natural Cys(I)/Ser isoform. The implications of the existence and expression of such Aox isoforms is discussed in the light of the hypothesised role for Aox in plant metabolism.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003080:Cold Temperature; D017931:DNA Primers; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant; D007527:Isoenzymes / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D018551:Solanum lycopersicum / Q000201:enzymology*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D005810:Multigene Family; D010088:Oxidoreductases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D000099188:Alternative Oxidase
chemical_list: D017931:DNA Primers; D007527:Isoenzymes; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D011994:Recombinant Proteins; D000099188:Alternative Oxidase