The Pigment--Protein Complexes of Photosynthetic Membranes of the Cyanobacterium Synechocystis sp. The Effect of Iron Deficiency

V. L. Tetenkin,^1,2 B. A. Gulyaev,¹ and V. M. Golitsin¹

¹School of Biology, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (7-095) 939-11-15; E-mail: Rubin@biophys.bio.msu.ru

²To whom correspondence should be addressed.

Submitted November 5, 1996; revision submitted December 16, 1996.

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The effect of accumulation of the pigment complex CP36 on the ratio between pigment--protein complexes was studied under various cultivation conditions of Synechocystis sp. PCC, 6803, wild type, and mutants Delta-2 (lacking PS2) and Delta-3 (lacking PS1); Synechocystis sp. BO 8402 (lacking phycobilisomes) and BO 9201 (a derivative of 8402 strain with phycobilisomes). The concentration of iron in the medium determines the content of CP36, which does not depend on the intensity of illumination during growth. Strain 8402 compensates the deficit of light-harvesting antenna of PS2 by synthesizing large amounts of PS2 complex. Under conditions of moderate iron deficiency the studied strains including mutants that do not contain one of the photosystems accumulate CP36; a sole exception was BO 8402. The content of phycobiliproteins was not decreased and the concentrations of both photosystems decreased proportionally. The content of PS2 monomers per phycobilisome decreased from 2-3 to 1. CP36 effectively transfers the electron excitation energy to both photosystems but it is predominantly connected with photosystem 2. This suggests that CP36 can stabilize the PS2 complex and can be an evolutionary precursor of the light-harvesting structures of higher plants.

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KEY WORDS: photosynthesis, pigment--protein complex, iron deficiency, photosystems 1 and 2, Synechocystis sp., CP36, CP43', migration of energy.

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