Structure of the chloroplast gene for the precursor of the Mr 32,000 photosystem II protein from mustard (Sinapis alba L.).

The nucleotide sequence of the mustard chloroplast gene for the precursor of the Mr 32,000 photosystem II protein is presented. A comparison with the corresponding genes from spinach and Nicotiana debneyi (14) reveals less than 5% nucleotide divergence in the coding region. The derived protein of mustard differs from the corresponding proteins by three amino acid positions at the C-terminus. We have defined the presumed transcription start and termination sites of the mustard gene. Upstream from the start site are sequences typical of a prokaryotic promoter and, also, a sequence that resembles the eukaryotic 'TATA' box. A search for intrastrand base pairing revealed stem-loop secondary structure at the transcription start and termination sites and in the region preceding the presumed promoter. This latter region is a 69-base-pair sequence element unique to the 5'flanking sequence of the mustard gene.