Localization and nucleotide sequence of the gene for the 8 kDa subunit of photosystem I in pea and wheat chloroplast DNA.

The gene for the 8 kDa subunit of photosystem I has been located in the small single copy region of wheat chloroplast DNA by coupled transcription-translation of cloned fragments of DNA and by DNA sequence analysis. The pea gene for this subunit was located in pea chloroplast DNA by using the wheat gene as a probe. The location was confirmed by immunoprecipitation of the products of coupled transcription-translation of cloned DNA with antiserum raised against the small subunits of pea photosystem I and by DNA sequence analysis. The deduced amino acid sequences of the pea and wheat proteins are identical in seventy-six out of the eighty-one amino acid residues. There are nine conserved cysteine residues, eight of which are arranged in the primary structure in a similar way to those in bacterial ferredoxins containing two 4Fe-4S centres, suggesting that the polypeptide binds iron sulphur centres A and B of photosystem I.