Subunit III (Psa-F) of photosystem I reaction center of the C4 dicotyledon Flaveria trinervia.

An immunological survey of C3, C4 and C3-C4-intermediate Flaveria species showed that subunit III (PsaF) of the photosystem I reaction center (PSI-RC) is present in all these species. This was confirmed by the isolation of the gene encoding the PSI-RC subunit III (PsaF) from Flaveria trinervia, the first psaF gene to be isolated from a C4 plant. The deduced amino acid sequence showed a high degree of similarity to the corresponding protein of spinach which is a C3 species. A region of 17 hydrophobic amino acids in the C-terminal part of the F. trinervia protein was found to be especially conserved in all PsaF proteins studied so far (cyanobacteria and Chlamydomonas).