The Eight-amino Acid Internal Loop of PSI-C Mediates Association of Low Molecular Mass Iron-Sulfur Proteins with the P700-FXCore in Photosystem IThe Journal of Biological Chemistry (1998)
The PSI-C subunit of photosystem I (PS I) shows similarity to soluble 2[4Fe–4S] ferredoxins. PSI-C contains an eight residue internal loop and a 15 residue C-terminal extension which are absent in the ferredoxins. The eight-residue loop has been shown to interact with PSI-A/PSI-B (Naver, H., Scott, M. P., Golbeck, J. H., Møller, B. L., and Scheller, H. V. (1996)J. Biol. Chem. 271, 8996–9001). Four mutant proteins were constructed. Two were modified barley PSI-C proteins, one lacking the loop and the C terminus (PSI-Ccore) and one where the loop replace the C-terminal extension (PSI-CcoreLc-term). Two were modifiedClostridium pasteurianum ferredoxins, one with the loop of barley PSI-C and one with both the loop and the C terminus of PSI-C. Wild-type proteins and the mutants were used to reconstitute barley P700-FX cores lacking PSI-C, -D, and-E. Western blotting showed that PSI-CcoreLc-term binds to PS I, whereas PSI-Ccore does not. Without PSI-D the PSI-CcoreLc-term mutant accepts electrons from FX in contrast to PSI-C mutants without the loop. Flash photolysis of P700-FX cores reconstituted with C. pasteurianum ferredoxin showed that only the ferredoxin mutants with the loop accepted electrons from FX. From this, it is concluded that the loop of PSI-C is necessary and sufficient for the association between PS I and PSI-C, and that the loop is functional as an interaction domain even when positioned at the C terminus of PSI-C or on a low molecular mass, soluble ferredoxin.
Publication DateJuly 24, 1998
Citation InformationHelle Naver, M. Paul Scott, John H. Golbeck, Carl Erik Olsen, et al.. "The Eight-amino Acid Internal Loop of PSI-C Mediates Association of Low Molecular Mass Iron-Sulfur Proteins with the P700-FXCore in Photosystem I" The Journal of Biological Chemistry Vol. 273 Iss. 30 (1998) p. 18778 - 18783
Available at: http://works.bepress.com/paul-scott/47/