Interaction between photosystem I and ferredoxin. Identification by chemical cross-linking of the polypeptide which binds ferredoxin

Abstract

Ferredoxin has been effectively cross-linked to photosystem I complex by treatment of purified particles or thylakoids with N-ethyl-3-(3-dimethylaminopropyl)carbodiimide, a zero-length cross-linker which stabilizes protein-protein electrostatic interactions. Analysis of photosystem I polypeptide composition after such a treatment showed a specific decrease of the 20-kDa subunit and the appearance of a new component of about 42 kDa which was recognized by the anti-ferredoxin antibody. Cross-linking of ferredoxin to thylakoids allowed the membrane preparation to photoreduce cytochrome c without requiring exogenous ferredoxin, whereas photosystem I particles purified from treated thylakoids were inactivated in the NADP' photoreduction activity. From these results, it can be inferred that the polypeptide of 20 kDa is the photosystem I subunit which interacts with ferredoxin during the photosynthetic electron transport.Electron transfer between photosystem I and NADP' in the photosynthetic chain, is mediated by ferredoxin and ferredoxin -NADPt reductase. Much is known on the interactions between the latter proteins [l -31, considerably less on the interactions between ferredoxin and PS I. Photosystem I is a membrane-spanning protein complex containing several polypeptides as well as six redox centers (P700, Ao, Al, X, A, B) (for recent reviews, see [4, 51). It has been suggested by Malkin [4, 61 that the electron donor of PS I to ferredoxin is the [4Fe-4S] iron-sulfur center A which seems closely associated with the [4Fe-4S] center B, possibly on the same polypeptide [7]. Association of such centers with specific PS

Identification of photosystem I components from the cyanobacterium, Synechococcus vulcanus by N‐terminal sequencing

“…This subunit is believed to interact with ferredoxin based on crosslinking experiments [30]. Corresponding genes have been isolated in Synechocystis, spinach and tomato and designated psaD [ 15,17,21 ].…”

Mutations of Glu92 in Ferredoxin I from Spinach Leaves Produce Proteins Fully Functional in Electron Transfer but Less Efficient in Supporting NADP+ Photoreduction

“…NADP' and cytochrome c photoreduction were performed with hypotonically washed spinach thylakoids prepared as described (Zanetti and Merati, 1987), except that 50 mM Tricine pH 7.8 was used as buffer. Chlorophyll (Chl) was determined according to Arnon (1949).…”

Purification and membrane topology of PSI‐D and PSI‐E, two subunits of the photosystem I reaction center

“…Background level for each coated immunoglobulin was obtained by revealing with the same immunoglobulin; no Stepwise extraction with NaSCN followed by electrophoresis on a type I gel. After transfer to Immobilon, the membrane was either stained with Coomassie blue (lanes [1][2][3][4] or reacted with a mixture of PSI-D and PSI-E antibodies (lanes [5][6][7][8]. Starting thylakoids (lanes 1, 5 ) ; supcrnatants of successive extractions with 1 M NaSCN (lane 2,6), and 2 M NaSCN (lane 3,7); residual membranes after the final extraction (lanes 4,8).…”