Suborganellar localisation and effect of light on Helianthus tuberosus chloroplast transglutaminases and their substrates
| Autor: | M. Della Mea, L. Dall'Agata, Donatella Serafini-Fracassini, I. Claparols, Luca Dondini, Mirko Gastaldelli, Roberto Bassi, A. Di Sandro, S. Del Duca |
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| Rok vydání: | 2003 |
| Předmět: |
Chloroplasts
Light Tissue transglutaminase Ribulose-Bisphosphate Carboxylase Photosynthetic Reaction Center Complex Proteins macromolecular substances Plant Science Thylakoids Substrate Specificity chemistry.chemical_compound Polyamines Genetics Carbon Radioisotopes Helianthus chemistry.chemical_classification Transglutaminases biology RuBisCO Photosystem II Protein Complex food and beverages Darkness biology.organism_classification Chloroplast Chloroplast stroma Enzyme chemistry Biochemistry Thylakoid biology.protein Polyamine |
| Zdroj: | Scopus-Elsevier |
| ISSN: | 1432-2048 0032-0935 |
| Popis: | The light stimulation of transglutaminase (TGase EC 2.3.2.13) activity was verified by incubating isolated chloroplasts of Helianthus tuberosus L. continuously or for alternate periods of light or dark (light/dark and dark/light). The first 10 min of incubation always represented the critical period. Light-harvesting complexes of photosystem II (LHCII) were more intensely labelled by (14)C-polyamines under light and light/dark than under dark and dark/light conditions. Chloroplasts were fractionated into thylakoid- and stroma-enriched fractions in which multiple TGase forms and substrates were found. Antibodies against TGase recognised 58- and 24-kDa bands in thylakoids and a 150-kDa band in the stroma. The latter, and its 150-kDa fraction, catalysed the conjugation of 14C-polyamines to Rubisco. In both fractions (thylakoid-pre and stroma-pre) the analysis of polyamine glutamyl derivatives showed a significant light-affected conjugation of polyamines to endogenous proteins. Alternatively, entire chloroplasts were incubated and afterwards their sub-fractions were isolated (thylakoid-post and stroma-post). The PSII and LHCII complexes were more intensely immunodetected in thylakoid-post than in thylakoid-pre, especially under dark conditions. Conversely, the conjugation of polyamines to thylakoid proteins was clearly light-stimulated in thylakoid-post, and much less in thylakoid-pre. Stroma-pre proteins were poorly polyamine-conjugated and not light-affected; on the contrary, stroma-post proteins were much more polyamine-modified and strongly light-stimulated. Thus, the light-activated conjugation depends mainly on the presence of the thylakoid fraction during the assay. The protective effect on chloroplasts under photo-damage, stress or senescence conditions attributed in the literature to free polyamines is discussed with regard to the occurrence of polyamine conjugates catalysed by TGases. |
| Databáze: | OpenAIRE |
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