Reconstitution of Barley Photosystem I with Modified PSI-C Allows Identification of Domains Interacting with PSI-D and PSI-A/BThe Journal of Biological Chemistry (1996)
The PSI-C subunit of photosystem I shows similarity to soluble 2[4Fe-4S] ferredoxins. Alignment analysis clearly shows that PSI-C contains an 8-residue internal loop and a 15-residue C-terminal extension that are absent in the ferredoxins. The remaining residues in PSI-C are likely to be folded in a way similar to the soluble 2[4Fe-4S] ferredoxins. Two modified PSI-C subunits lacking either the 8-residue loop or 10 residues of the C terminus were expressed in Escherichia coli and used to reconstitute a barley P700-F core prepared to specifically lack PSI-C, PSI-D, and PSI-E. As shown by EPR spectroscopy, the modified proteins carry two [4Fe-4S] clusters with characteristics similar to those of native PSI-C. Western blot analysis of the reconstituted photosystem I complexes showed that the modified PSI-C proteins bind to the P700-F core. Flash photolysis revealed that in photosystem I complexes reconstituted in the presence of PSI-D with the C-terminally deleted PSI-C, the F/Fback-reaction was less efficiently restored than with wild-type PSI-C. The loop-deleted PSI-C was even less efficient. We attribute these differences to altered binding properties of the modified proteins. Comparison of reconstitutions performed in the presence and absence of PSI-D shows that the loop-deleted PSI-C is unable to bind without PSI-D, whereas the C-terminally deleted PSI-C binds only weakly with PSI-D. These results imply that the internal loop of PSI-C interacts with the PSI-A/B heterodimer and that the C terminus of PSI-C interacts with PSI-D.
Publication DateApril 12, 1996
Citation InformationHelle Naver, M. Paul Scott, John H. Golbeck, Birger L. Møller, et al.. "Reconstitution of Barley Photosystem I with Modified PSI-C Allows Identification of Domains Interacting with PSI-D and PSI-A/B" The Journal of Biological Chemistry Vol. 271 Iss. 15 (1996) p. 8996 - 9001
Available at: http://works.bepress.com/paul-scott/49/