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Searching for microtubule inner proteins
Bočan, Václav ; Libusová, Lenka (advisor) ; Varga, Vladimír (referee)
Diploma thesis Searching for microtubule inner proteins Bc. Václav Bočan Abstract Microtubules (MTs) - cylindrical polymers of α- and β-tubulin - maintain numerous irreplaceable func- tions in all eukaryotic cells. For this complex involvement of MTs in many cellular processes, precise tuning of their post-translational modifications, polymerization state, and interactome is crucial. Recently, a new mode of interactions with MTs was discovered - several microtubule inner proteins (MIPs) can enter the lumen of MTs. Little is known about MIPs in dynamic MTs in the cytoplasmic network. Only two proteins have been shown to bind to the inside of dynamic MTs so far: αTAT1 and MAP6; other proteins have been suggested to. Stabilised MTs, like the axoneme of the flagellum, contain dozens of orderly bound MIPs in the lumen and new ones are being added. MIPs are believed to play a role during axonemal assembly and to increase the stiffness required for flagellar beating. This diploma thesis investigated MIPs in both dynamic and axonemal MTs. In the first part of the thesis, the goal was to identify candidates for new MIPs in the dynamic MTs by two independent approaches - proximity-labelling by promiscuous biotin ligase using αTAT1 and MAP6 as baits, and direct isolation of MTs from cells and washing away outer...
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Microtubule inner proteins
Bočan, Václav ; Libusová, Lenka (advisor) ; Sulimenko, Vadym (referee)
Microtubules are a prominent part of the cytoskeletal network in eukaryotic cells. They are involved in nearly all cellular processes, e.g. in vesicular trafficking, signal transduction, locomotion, or cell morphogenesis. To discharge that many functions, precise regulation of microtubule dynamics and architecture is essential. Such regulation is maintained by various microtubule-associated proteins, which usually bind from the outside. However, several proteins were found to bind in the lumen of microtubules. These microtubule inner proteins were shown to function either as post-translational modifiers of tubulin or stabilizers in time- persistent microtubular structures. A few inner proteins were identified, but our understanding of their attributes is still incomplete. This thesis summarizes current knowledge of microtubule inner proteins. The scope is focused on their enzymatic and structural features. Tubulin acetyltransferase represents the enzymatic MIPs. Possible ways of lumen entry and impact on the tubulin lattice are described. Next, the structural roles of proteins inside microtubules, most prominent in the axoneme, are outlined. The relevance of microtubule inner proteins for cytoskeletal functions, flagellar motility, and future perspectives are discussed at the end.
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