Light stress-regulated two-helix proteins in Arabidopsis thaliana related to the chlorophyll a/b-binding gene family.
The chlorophyll a/b, chlorophyll a/c, and chlorophyll a/a light-harvesting proteins are part of an extended gene family that also includes the transiently expressed stress proteins, the Elips (early light-induced proteins). Four Elip homologue proteins, encoded by single-copy nuclear genes, have been identified in the Arabidopsis thaliana database. These proteins were divided into two groups according to the expression pattern under light-stress conditions and the predicted secondary structure. Group one included two members of the Elip family with three predicted transmembrane helices and a gene expression strictly related to light stress. Group two included two proteins, the Seps (stress-enhanced proteins), which possessed two predicted transmembrane segments. The transcripts of Sep1 and Sep2 were present under low light conditions, but their level increased 4- to 10-fold during illumination of plants with high-intensity light. Preliminary data indicated that the induced transcripts were translated in vivo. Other physiological stress conditions, such as cold, heat, desiccation, salt, wounding, or oxidative stress, did not significantly influence the expression of Sep genes. In vitro import of radioactively labeled precursors of Seps into isolated chloroplasts confirmed the thylakoid membrane localization of these proteins. Considering the predicted protein structure and homology to other pigment-antenna proteins, the two-helix Seps might represent an evolutionary missing link between the one- and three-helix antenna proteins present in pro- and eukaryota.
Heddad
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Department of Biochemistry, Arrhenius Laboratories for Natural Sciences, Stockholm University, S-10691 Stockholm, Sweden.
Adamska
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D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics*; D002736:Chloroplasts / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D018745:Genome, Plant; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D005810:Multigene Family; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D029681:Arabidopsis Proteins; C490217:CAB1 protein, Arabidopsis; D002352:Carrier Proteins; C078410:ELIP protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D020033:Protein Isoforms