| Summary: | During my PhD course, I have worked on and contributed to three different projects with an unique goal, that is the study of the evolutionary strategies and of the molecular mechanisms responsible of cold adaptation in the Antarctic ciliate Euplotes focardii. To reach this aim I have investigated: 1. The mechanisms that allow an efficient protein synthesis in the cold by analyzing the genes encoding the acidic ribosomal proteins P0 and P2 (Chapter 1); they are implicated in the formation of the lateral protuberance on the 60S ribosomal subunit, the so-called ribosomal stalk, which is involved in protein synthesis regulation through interaction with soluble translation factors and in GTP hydrolysis control during elongation steps. Moreover, since the function of the stalk and the amino acid sequences of the proteins of which it is composed are very conserved from Prokaryotes to upper Eukaryotes, by the analysis of the P proteins it could be possible to get new information on the phylogenetic origin of Eukaryotes, a very discussed but yet unresolved theme. 2. The molecular systems responsible of microtubule polymerization, nucleation and stability at low temperatures, since microtubules are structures involved in many fundamental life processes, such as cell division, intracellular transport and motility. In particular, my work focuses on microtubule nucleation in the cold, as to date this phenomenon has not been studied, while the polymerization has been deeply analyzed in Euplotes focardii and mainly in Antarctic fish. 3. The folding mechanisms employed by the cytoskeletal proteins through a comparative study between two divergent isotypes of β-tubulin in Euplotes focardii (Chapter 3).
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