Effect of low temperature on the protein content of the thylakoid lumen of Arabidopsis thaliana

Abstract

Based on recent results, a new picture of the thylakoid lumen of higher plant chloroplasts is emerging. The lumenal compartment is no longer only a space for the charge balance during ATP production but seems to play an important role in regulating the stability, function and assembly of the different photosynthetic complexes. Using a proteomic approach we have performed a systematic analysis of the protein content of the chloroplast lumen of Arabidopsis thaliana. The lumen fraction was isolated and proteins separated with two dimensional gel electrophoresis. Proteins were analysed with MALDI-TOF MS and micro sequencing. From our data, we estimate that the thylakoid lumen contains 60 to 80 soluble proteins. Besides the classical lumenal proteins such as PsbO, PsbP, PsbQ and plastocyanin, we detected a novel plastocyanin and isoforms of PsbO and PsbQ. In addition, we identified a group of novel PsbP-like proteins and a peroxidase homologue. We also found several proteases, peptidyl-prolyl cis-trans isomerases and a large group of novel proteins with unknown functions. The possible roles of the different groups of lumenal proteins are discussed.