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Aseeva, Elena (2005): Vipp1 structure and function in cyanobacteria and chloroplasts. Dissertation, LMU München: Faculty of Biology
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Abstract

The vesicle inducing protein in plastids 1 (Vipp1) is an essential factor for the development and maintenance of the thylakoid membrane. Depletion of Vipp1 in both Arabidopsis and Synechocystis mutants severely affects their ability to form thylakoids and consequently to perform photosynthesis. This work focuses on structural and functional properties of Vipp1. It was shown that Vipp1 assembles into a homooligomeric complex of ca. 2000 kDa. The presence of the Vipp1 complex was detected in cyanobacteria, green algae and higher plants, thereby identifying oligomerization as an essential feature for the function of Vipp1. A detailed computer analysis of Vipp1 secondary structure in different organisms revealed functionally important characteristics of the protein and allowed to discern specific features of its C-terminal domain. Based on the structural analysis, biochemical characterization of Vipp1 domains was carried out. It appeared that the PspA-like domain of Vipp1 is responsible for both complex formation and localisation of Vipp1 at the inner envelope of chloroplasts while the C-terminal domain is not involved in these processes. In order to closer elucidate the function of Vipp1, an analysis of Arabidopsis plants with moderate deficiency in Vipp1 protein level was performed. From results obtained in this analysis it can be proposed that Vipp1 acts at the initial stages of thylakoid biogenesis. Oligomerization of Vipp1 appeared to be a prerequisite for the process of thylakoid formation to commence. Moreover, the extent of thylakoid membrane formation is directly correlated to the amount of Vipp1 protein available in the chloroplast.