A Medicago truncatula homoglutathione synthetase is derived from glutathione synthetase by gene duplication.
Glutathione (GSH) and homo-GSH (hGSH) are the major low-molecular weight thiols synthesized in Medicago truncatula. Two M. truncatula cDNAs (gshs1 and gshs2) corresponding to a putative GSH synthetase (GSHS) and a putative hGSH synthetase (hGSHS) were characterized. Heterologous expression of gshs1 and gshs2 cDNAs in an Escherichia coli strain deficient in GSHS activity showed that GSHS1 and GSHS2 are a GSHS and an hGSHS, respectively. Leucine-534 and proline-535 present in hGSHS were substituted by alanines that are conserved in plant GSHS. These substitutions resulted in a strongly stimulated GSH accumulation in the transformed E. coli strain showing that these residues play a crucial role in the differential recognition of beta-alanine and glycine by hGSHS. Phylogenetic analysis of GSHS2 and GSHS1 with other eukaryotic GSHS sequences indicated that gshs2 and gshs1 are the result of a gene duplication that occurred after the divergence between Fabales, Solanales, and Brassicales. Analysis of the structure of gshs1 and gshs2 genes shows they are both present in a cluster and in the same orientation in the M. truncatula genome, suggesting that the duplication of gshs1 and gshs2 occurred via a tandem duplication.
Frendo
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P
Laboratoire de Biologie Végétale et Microbiologie, Centre National de la Recherche Scientifique, Formation de Recherche en Evolution 2294, Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice cedex 2, France. frendo@unice.fr
Jiménez
M J
MJ
Mathieu
C
C
Duret
L
L
Gallesi
D
D
Van de Sype
G
G
Hérouart
D
D
Puppo
A
A
D000595:Amino Acid Sequence; D000818:Animals; D002874:Chromosome Mapping; D018076:DNA, Complementary / Q000032:analysis; D018744:DNA, Plant / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics; D020440:Gene Duplication; D017343:Genes, Plant; D005981:Glutathione Synthase / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D000455:Medicago sativa / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D010453:Peptide Synthases / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D020080:Tandem Repeat Sequences
D018076:DNA, Complementary; D018744:DNA, Plant; D010453:Peptide Synthases; C402171:homoglutathione synthase; D005981:Glutathione Synthase