Green plant photosystem I binds light-harvesting complex I on one side of the complex.
We report a structural characterization by electron microscopy of green plant photosystem I solubilized by the mild detergent n-dodecyl-alpha-D-maltoside. It is shown by immunoblotting that the isolated complexes contain all photosystem I core proteins and all peripheral light-harvesting proteins. The electron microscopic analysis is based on a large data set of 14 000 negatively stained single-particle projections and reveals that most of the complexes are oval-shaped monomers. The monomers have a tendency to associate into artificial dimers, trimers, and tetramers in which the monomers are oppositely oriented. Classification of the dimeric complexes suggests that some of the monomers lack a part of the peripheral antenna. On the basis of a comparison with projections from trimeric photosystem I complexes from cyanobacteria, we conclude that light-harvesting complex I only binds to the core complex at the side of the photosystem I F/J subunits and does not cause structural hindrances for the type of trimerization observed in cyanobacterial photosystem I.
Boekema
E J
EJ
Groningen Biotechnology and Biomolecular Sciences Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Jensen
P E
PE
Schlodder
E
E
van Breemen
J F
JF
van Roon
H
H
Scheller
H V
HV
Dekker
J P
JP
D002734:Chlorophyll / Q000737:chemistry; D002850:Chromatography, Gel; D019281:Dimerization; D015151:Immunoblotting; D045342:Light-Harvesting Protein Complexes; D008854:Microscopy, Electron; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000276:immunology / Q000648:ultrastructure; D045331:Photosystem I Protein Complex; D018724:Spinacia oleracea / Q000737:chemistry*; D020524:Thylakoids / Q000737:chemistry / Q000276:immunology / Q000648:ultrastructure
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D002734:Chlorophyll