Analysis of cDNA Clones Encoding the Entire Ferredoxin I Precursor Polypeptide from Spinach

We report the isolation and characterization of a recombinant cDNA phage from a lambda gt11 expression library made from polyadenylated spinach RNA that encodes the entire precursor polypeptide of ferredoxin I. The deduced sequence predicts a molecular mass of 10.5 kDa (97 amino acid residues) for the mature protein and a transit peptide of 50 residues (5.2 kDa). In vitro synthesized ferredoxin precursor was used for import experiments with isolated unbroken spinach chloroplasts. The polypeptide was correctly directed to the organelle stroma and processed to the size of the mature protein. Northern analysis indicates a mRNA size of ca. 850 nucleotides which is close to the size of the cDNA insert (ca. 700 bp).