Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.2.1.22 (cystathionine beta-synthase)
 965 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cysteine synthase (CSase) [O-acetyl-L-serine acetate-lyase (adding hydrogen sulfide), EC 4.2.99.8] catalyzes the formation of L-cysteine, the key step in sulfur assimilation in plants, from O-acetyl-L-serine and hydrogen sulfide. We report here the isolation and characterization of cDNA clones encoding cysteine synthase from spinach (Spinacia oleracea L.). Internal peptide sequences were obtained from V8 protease-digested fragments of purified CSase. A lambda gt10 cDNA library was constructed from poly(A)+ RNA of young green leaves of spinach. Screening with two synthetic mixed nucleotides encoding the partial peptide sequences revealed 19 positively hybridized clones among 2 x 10(5) clones. Nucleotide sequence analysis of two independent cDNA clones revealed a continuous open reading frame encoding a polypeptide of 325 amino acids with a calculated molecular mass of 34,185 Da. Sequence comparison of the deduced amino acids revealed 53% identity with CSases of Escherichia coli and Salmonella typhimurium. Sequence homology was also observed with other metabolic enzymes for amino acids in bacteria and yeast and with rat hemoprotein H-450. A bacterial expression vector was constructed and could genetically complement an E. coli auxotroph that lacks CSases. The accumulation of functionally active spinach CSase in E. coli was also demonstrated by immunoblotting and assaying enzymatic activity. Southern hybridization analysis showed the presence of two to three copies of the cDNA sequence in the genome of spinach. RNA blot hybridization suggested constitutive expression in leaves and roots of spinach.
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PMID:Molecular cloning and bacterial expression of cDNA encoding a plant cysteine synthase. 151 33

The cDNA clones that encode a putative mitochondrion-localizing isoform of cysteine synthase (O-acetyl-L-serine(thiol)-lyase, O-acetyl-L-serine acetate-lyase (adding hydrogen sulfide), EC 4.2.99.8), which is denoted as cysteine synthase C, were isolated from spinach (Spinacia oleracea L.). The cDNA encodes a polypeptide of 368 amino acids containing a putative transit peptide of 30-40 amino acids at the N terminus. This leader peptide sequence exhibited several structural features common to other mitochondrion-targeting transit peptides. Homology was also detected between the putative transit peptide sequence of cysteine synthase C and other mitochondrion-targeting leader sequences. A deduced amino acid sequence of cysteine synthase C exhibited a homology of 61% with cytoplasmic isoform A and 63% with chloroplastic isoform B. A bacterial expression vector of the cDNA clone could genetically complement an Escherichia coli auxotroph lacking cysteine synthase loci and could produce the functionally active and immunoreactive cysteine synthase in E. coli. DNA blot hybridization analysis showed the presence of one or two copies of cysC gene in the genome of spinach. RNA blot hybridization analysis indicated that the expression level of cysC gene was lower than those of cysA and cysB and that the mode of cysC expression was constitutive in green and etiolated seedlings of spinach. The molecular evolutionary study of cysteine synthase proteins from plants and bacteria suggested that a common ancestor cysteine synthase gene has evolved into five cysteine synthase gene families, plant isoform A family, plant isoform B family, plant isoform C family, bacterial cysK family, and bacterial cysM family.
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PMID:Isolation and characterization of cDNA that encodes a putative mitochondrion-localizing isoform of cysteine synthase (O-acetylserine(thiol)-lyase) from Spinacia oleracea. 796 55