The association of the antenna system to photosystem I in higher plants. Cooperative interactions stabilize the supramolecular complex and enhance red-shifted spectral forms.
We report on the association of the antenna system to the reaction center in Photosystem I. Biochemical analysis of mutants depleted in antenna polypeptides showed that the binding of the antenna moiety is strongly cooperative. The minimal building block for the antenna system was shown to be a dimer. Specific protein-protein interactions play an important role in antenna association, and the gap pigments, bound at the interface between core and antenna, are proposed to mediate these interactions Gap pigments have been characterized by comparing the spectra of the Photosystem I to those of the isolated antenna and core components. CD spectroscopy showed that they are involved in pigment-pigment interactions, supporting their relevance in energy transfer from antenna to the reaction center. Moreover, gap pigments contribute to the red-shifted emission forms of Photosystem I antenna. When compared with Photosystem II, the association of peripheral antenna complexes in PSI appears to be more stable, but far less flexible and functional implications are discussed.
Morosinotto
Tomas
T
Dipartimento Scientifico e Tecnologico, Università di Verona, 37134 Verona, Italy.
Ballottari
Matteo
M
Klimmek
Frank
F
Jansson
Stefan
S
Bassi
Roberto
R
D017360:Arabidopsis / Q000737:chemistry / Q000502:physiology; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000502:physiology*; D015394:Molecular Structure; D045331:Photosystem I Protein Complex / Q000502:physiology*; D010860:Pigments, Biological / Q000737:chemistry; D011487:Protein Conformation; D011489:Protein Denaturation; D020524:Thylakoids / Q000737:chemistry / Q000378:metabolism
D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D010860:Pigments, Biological