Characterization of low molecular mass proteins of photosystem II by N‐terminal sequencing

The N‐terminal amino acid sequence of four chloroplast proteins with the apparent molecular masses of 3.7, 6.5, 7 and 8 kDa has been determined. Two of the proteins (6.5 and 7 kDa) turned out to have the same amino acid sequence. This sequence, and the sequence of the 3.7 kDa protein, did not correspond to any of the known chloroplast protein sequences, or to any of the open reading frames of the chloroplast genome. The 8 kDa protein, which could be distinguished from the cytochrome b‐559 band only at increased urea concentrations, was partially purified and found to be a degradation product of the extrinsic 16 kDa protein.