The gene for the 9 kd polypeptide, a possible apoprotein for the iron-sulfur centers A and B of the photosystem I complex, in tobacco chloroplast DNA.

The gene for the 9 kd polypeptide (a possible apoprotein for the iron-sulfur centers A and B) of photosystem I has been located in the small single-copy region of tobacco chloroplast DNA. This gene (psaC) was identified by comparing the N-terminal amino acid sequence of the spinach 9 kd polypeptide with the entire sequence of tobacco chloroplast genome. The gene organization is ndhE (101 codons)--263 bp spacer--psaC (81 codons)--94 bp spacer--ndhD (509 codons). Northern blot hybridization revealed that psaC is transcribed in the chloroplasts. The deduced amino acid sequence and secondary structure are presented. The predicted polypeptide is rich in cysteine residues and contains a unique repeated sequence.