CDNA CLONING AND EXPRESSION OF CYSTEINE SYNTHASE-B LOCALIZED IN CHLOROPLASTS OF SPINACIA-OLERACEA

The cDNA clones for cysteine synthase B, which is localized in chloroplasts of Spinacia oleracea L., were isolated by screening a library with synthetic oligonucleotides encoding a partial peptide sequence of the purified protein. Nucleotide sequence analysis revealed an open reading frame encoding a polypeptide of 383 amino acids containing a putative transit peptide of 52 amino acids. A bacterial expression vector of the cDNA clone could genetically complement an Escherichia coli auxotroph lacking cysteine synthase and could produce the functionally active and immuno-reactive cysteine synthase in E. coli. RNA blot hybridization suggested that the transcripts were primarily accumulated in leaves of spinach.