title: Structural thermal adaptation of β-tubulins from the Antarctic psychrophilic protozoan Euplotes focardii.
abstract: Tubulin dimers of psychrophilic eukaryotes can polymerize into microtubules at 4°C, a temperature at which microtubules from mesophiles disassemble. This unique capability requires changes in the primary structure and/or in post-translational modifications of the tubulin subunits. To contribute to the understanding of mechanisms responsible for microtubule cold stability, here we present a computational structural analysis based on molecular dynamics (MD) and experimental data of three β-tubulin isotypes, named EFBT2, EFBT3, and EFBT4, from the Antarctic protozoon Euplotes focardii that optimal temperature for growth and reproduction is 4°C. In comparison to the β-tubulin from E. crassus, a mesophilic Euplotes species, EFBT2, EFBT3, and EFBT4 possess unique amino acid substitutions that confer different flexible properties of the polypeptide, as well as an increased hydrophobicity of the regions involved in microtubule interdimeric contacts that may overcome the microtubule destabilizing effect of cold temperatures. The structural analysis based on MD indicated that all isotypes display different flexibility properties in the regions involved in the formation of longitudinal and lateral contacts during microtubule polymerization. We also investigated the role of E. focardii β-tubulin isotypes during the process of cilia formation. The unique characteristics of the primary and tertiary structures of psychrophilic β-tubulin isotypes seem responsible for the formation of microtubules with distinct dynamic and functional properties.
authors.affiliation: Istituto di Tecnologie Biomediche-Consiglio Nazionale delle Ricerche, Segrate (MI), Italy. federica.chiappori@itb.cnr.it
authors.forename: Federica
authors.initials: F
authors.lastname: Chiappori
authors.forename: Sandra
authors.initials: S
authors.lastname: Pucciarelli
authors.forename: Ivan
authors.initials: I
authors.lastname: Merelli
authors.forename: Patrizia
authors.initials: P
authors.lastname: Ballarini
authors.forename: Cristina
authors.initials: C
authors.lastname: Miceli
authors.forename: Luciano
authors.initials: L
authors.lastname: Milanesi
mesh_terms: D000064:Acclimatization; D019943:Amino Acid Substitution; D000864:Antarctic Regions; D015152:Blotting, Northern; D002875:Chromosomes / Q000737:chemistry / Q000235:genetics; D002923:Cilia / Q000737:chemistry; D003080:Cold Temperature; D003198:Computer Simulation; D016812:Euplotes / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D057927:Hydrophobic and Hydrophilic Interactions; D056004:Molecular Dynamics Simulation; D009391:Nephelometry and Turbidimetry; D058105:Polymerization; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D016053:RNA, Protozoan / Q000737:chemistry / Q000235:genetics; D014158:Transcription, Genetic; D014404:Tubulin / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D015800:Protozoan Proteins; D016053:RNA, Protozoan; D014404:Tubulin