Structural changes and lateral redistribution of photosystem II during donor side photoinhibition of thylakoids.
The structural and topological stability of thylakoid components under photoinhibitory conditions (4,500 microE.m-2.s-1 white light) was studied on Mn depleted thylakoids isolated from spinach leaves. After various exposures to photoinhibitory light, the chlorophyll-protein complexes of both photosystems I and II were separated by sucrose gradient centrifugation and analysed by Western blotting, using a set of polyclonals raised against various apoproteins of the photosynthetic apparatus. A series of events occurring during donor side photoinhibition are described for photosystem II, including: (a) lowering of the oligomerization state of the photosystem II core; (b) cleavage of 32-kD protein D1 at specific sites; (c) dissociation of chlorophyll-protein CP43 from the photosystem II core; and (d) migration of damaged photosystem II components from the grana to the stroma lamellae. A tentative scheme for the succession of these events is illustrated. Some effects of photoinhibition on photosystem I are also reported involving dissociation of antenna chlorophyll-proteins LHCI from the photosystem I reaction center.
Barbato
R
R
Dipartimento di Biologia, Universita di Padova, Italy.
Friso
G
G
Rigoni
F
F
Dalla Vecchia
F
F
Giacometti
G M
GM
D001059:Apoproteins / Q000032:analysis; D001426:Bacterial Proteins / Q000378:metabolism / Q000528:radiation effects; D001692:Biological Transport / Q000528:radiation effects; D002736:Chloroplasts / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D007425:Intracellular Membranes / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D008027:Light / Q000009:adverse effects*; D045342:Light-Harvesting Protein Complexes; D008345:Manganese / Q000378:metabolism; D008954:Models, Biological; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010944:Plants / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure; D011487:Protein Conformation / Q000528:radiation effects; D013347:Subcellular Fractions / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure
D001059:Apoproteins; D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D008345:Manganese