The evolution of light stress proteins in photosynthetic organisms.

The Elip (early light-inducible protein) family in pro- and eukaryotic photosynthetic organisms consists of more than 100 different stress proteins. These proteins accumulate in photosynthetic membranes in response to light stress and have photoprotective functions. At the amino acid level, members of the Elip family are closely related to light-harvesting chlorophyll a/b-binding (Cab) antenna proteins of photosystem I and II, present in higher plants and some algae.

Differential expression and localization of early light-induced proteins in Arabidopsis.

The early light-induced proteins (Elips) in higher plants are nuclear-encoded, light stress-induced proteins located in thylakoid membranes and related to light-harvesting chlorophyll (LHC) a/b-binding proteins. A photoprotective function was proposed for Elips. Here we showed that after 2 h exposure of Arabidopsis (Arabidopsis thaliana) leaves to light stress Elip1 and Elip2 coisolate equally with monomeric (mLhcb) and trimeric (tLhcb) populations of the major LHC from photosystem II (PSII) as based on the Elip:Lhcb protein ratio.

Multiple evidence for nucleotide metabolism in the chloroplast thylakoid lumen.

The apparatus of photosynthetic energy conversion in chloroplasts is quite well characterized with respect to structure and function. Light-driven electron transport in the thylakoid membrane is coupled to synthesis of ATP, used to drive energy-dependent metabolic processes in the stroma and the outer surface of the thylakoid membrane. The role of the inner (luminal) compartment of the thylakoids has, however, remained largely unknown although recent proteomic analyses have revealed the presence of up to 80 different proteins.

Light stress-induced one-helix protein of the chlorophyll a/b-binding family associated with photosystem I.

The superfamily of light-harvesting chlorophyll a/b-binding (Lhc) proteins in higher plants and green algae is composed of more than 20 different antenna proteins associated either with photosystem I (PSI) or photosystem II (PSII). Several distant relatives of this family with conserved chlorophyll-binding residues and proposed photoprotective functions are induced transiently under various stress conditions. Whereas "classical" Lhc proteins contain three-transmembrane alpha-helices, their distant relatives span the membrane with between one and four transmembrane segments.