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Eur. J Biochem. 204, 1107-1114(1992) `cFEUS 1992

Summary: Eur. J Biochem. 204, 1107-1114(1992)
`cFEUS 1992
Protein phosphorylation and Mg2+ influence light harvesting
and electron transport in chloroplast thylakoid membrane material
containing only the chlorophyll-+binding light-harvesting complex
of photosystem I1 and photosystem I
Michael A. HARRISON and John F. ALLEN
Department of Pure and Applied Biology, University of Leeds, England
(ReceivedAugust 27/December 3, 1991) - EJB 91 1153
A material containing only photosystem I (PSI) and the chlorophyll-a/b-binding light-harvesting
complex of PSII (LHC-11) has been isolated from the chloroplast thylakoid membrane by solubiliza-
tion with Triton X-100. Fluorescence spectroscopy shows that, within the material, LHC-11iscoupled
to PSI for excitation-energy transfer and that this coupling is decreased by the presence of Mg2+,
which also decreased PSI electron transport specifically at limiting light intensity. Inclusion of
phosphorylated LHC-I1 within the material did not alter its structure, but gave decreased energy
transfer to PSI and inhibition of electron transport which was independent of light intensity, implying
effects of phosphorylation on both light harvesting and directly on electron transport. Inclusion of
Mg2+within the phosphorylated material gave decreased energy transfer, but slightly increased PSI
electron transport. A cation-induced direct promotion of PSI electron transport was also observed
in isolated PSI particles. The PSI/LHC-I1 material represents a model system for examining protein


Source: Allen, John F. - School of Biological and Chemical Sciences, Queen Mary, University of London


Collections: Renewable Energy; Biology and Medicine