Study of the Location of Low-Molecular Stress-Inducible Proteins that Protect the Photosynthetic Apparatus against Photodestruction

Abstract

An association of low molecular weight, light-inducible HliA/HliA stress proteins with thylakoid chlorophyll–protein complexes of the cyanobacterium Synechocystis sp. PCC 6803 was studied. It is shown via two-dimensional electrophoresis in PAAG, mass spectrometry, and Western blotting that these light-inducible HliA/HliB stress proteins are associated with monomers and trimeric photosystem I (PSI) сomplexes and the photosystem II (PSII) complex. This suggests that these proteins play a universal role in the protection of the photosynthetic apparatus from excess light. To evaluate the functions of Hli proteins and their effect on the photochemical activity of PSI, non-HliA/HliB cells were compared with cyanobacterial cells containing these proteins. It is shown that the PSI photochemical activity was three to four times lower in the absence of HliA/HliB proteins than in the presence of Hli proteins. This suggests that Hli proteins are important for the reaction to oxygen consumption in PSI with an artificial donor and acceptor, which indicates their role in the maintenance of optimal PSI activity.