title: Arabidopsis thaliana tryptophan synthase alpha: gene cloning, expression, and subunit interaction.
abstract: The tryptophan synthase alpha subunit catalyzes the conversion of indole-3-glycerolphosphate to indole, the penultimate reaction in the biosynthesis of the essential amino acid tryptophan. A cDNA encoding Arabidopsis thaliana tryptophan synthase alpha(TSA1) was isolated by complementation of an Escherichia coli delta trpA mutation and by polymerase chain reaction amplification from a cDNA library using degenerate primers. A TSA1 genomic clone was also isolated and 5 kb of the DNA sequence determined. A single sequence in the Arabidopsis genome with homology to the TSA1 cDNA was detected by high-stringency genomic Southern blot hybridization. In contrast under hybridization conditions of reduced stringency, one or two additional homologous sequences were observed. A 1.4 kb transcript was detected in wild-type RNA with the TSA1 cDNA as a probe. Several lines of evidence, including immunoaffinity chromatography, suggest that the active A. thaliana tryptophan synthase enzyme consists of a heterosubunit complex, presumably analogous to the prokaryotic alpha 2 beta 2 complex. Immunoblot analysis indicated that the plant alpha and beta subunits are present throughout development.
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D017343:Genes, Plant; D015151:Immunoblotting; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification; D016415:Sequence Alignment; D017421:Sequence Analysis; D014170:Transformation, Genetic; D014367:Tryptophan Synthase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D017931:DNA Primers; D011994:Recombinant Proteins; D014367:Tryptophan Synthase