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Structural and functional analysis of the reducing side of photosystem I
Author(s) -
Andersen Birgitte,
Koch Birgit,
Scheller Henrik Vibe
Publication year - 1992
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1992.tb08778.x
Subject(s) - ferredoxin , photosystem i , plastocyanin , chemistry , protein subunit , electron transfer , ferredoxin—nadp(+) reductase , hordeum vulgare , stereochemistry , biochemistry , biophysics , biology , photosystem ii , photochemistry , enzyme , photosynthesis , botany , poaceae , gene
Structural analysis of the reducing side of photosystem I (PSI) has been carried out using chemical cross‐linking and monospecific antibodies. Incubation of PSI isolated from barley (Hordeum vulgare L.) with the hydrophilic cross‐linking agent N‐ethyl‐3‐[3‐(dimethylamino) propyl]‐carbodiimide leads to cross‐linking of the PSI‐D subunit with the PSI‐E and PSI‐H subunits. In the presence of ferredoxin, cross‐linking results in the formation of cross‐linked products composed of PSI‐D, PSI‐E and ferredoxin and in a block in steady state NADP + photoreduction. No cross‐linking of ferredoxin occurs at elevated ionic strength or using heat‐denatured ferredoxin. Cross‐linking of ferredoxin does not inhibit electron transfer from plastocyanin to methyl viologen. Steady state NADP + photoreduction was analyzed in PSI or thyla‐koids incubated with antibodies against individual PSI subunits. Incubation with antibodies against PSI‐C, ‐H, ‐I, or ‐L had no effect on PSI activity, whereas antibodies against PSI‐D or PSI‐E had similar effects and caused a large decrease in activity. The results provide evidence that the PSI‐D and PSI‐E subunits are localized on the reducing side of PSI, forming a barrier between PSI‐C and the stroma as well as a docking site for ferredoxin. The PSI‐H subunit has an exposed, stromal domain but this does not appear to contribute to the ferredoxin docking.