58 research outputs found
Dynamics of an aminoacyl-tRNA synthetase complex assembly
Vjernost biosinteze proteina oÄuvana je toÄnim aminoaciliranjem specifiÄne transfer-RNA (tRNA) pripadnom aminokiselinom i dekodiranjem pojedine aminoacilirane tRNA na ribosomu. Aminoacil-tRNA-sintetaze kataliziraju prvu reakciju te Äesto stupaju u interakcije s drugim staniÄnim proteinima. U arheji Methanothermobacter thermautotrophicus arginil- i seril-tRNA-sintetaza (MtArgRS i MtSerRS) stupaju u prolaznu interakciju oblikujuÄi kompleks. Metodom afinitetnog suproÄiÅ”Äavanja i rezonancije povrÅ”inskih plazmona s krnjim oblicima MtArgRS pokazano je da MtSerRS prepoznaje N-terminalni dio ArgRS, s naglaskom na elemente zadužene za prepoznavanje pripadne tRNA. Krnji oblici delta89-ArgRS i deltaNtot-ArgRS zamjetno oslabljeno vežu i aminoaciliraju pripadnu tRNA. S obzirom na prisutnost reakcijskih prekursora pokazano je da serilacijski intermedijeri ne utjeÄu na stabilnost kompleksa ArgRS:SerRS. DapaÄe, molekula tRNASer može participirati u formiranju ternarnog kompleksa [SerRS:tRNASer]:ArgRS Äija je stabilnost usporediva s onom binarnog kompleksa SerRS:ArgRS. Nasuprot tome, interakcija ovih proteina osjetljiva je na dodatak potpuno modificirane tRNAArg, koja dovodi do disocijacije proteinskog kompleksa. Transkripcija MttRNAArg u bakteriji E. coli rezultira nastankom triju karakteristiÄnih molekulskih vrsta koje se razlikuju s obzirom na stupanj nadodanih posttranskripcijskih modifikacija. Istraživana arginil-tRNA-sintetaza aminoacilira takve supstrate s podjednakom uÄinkovitoÅ”Äu. Zanimljivo, SerRS inhibira arginilaciju loÅ”ijih supstrata, tj. manje modificiranih molekula tRNAArg. Uklanjanje djelomiÄno modificiranih tRNA iz procesa translacije pokazuje kako ovaj proteinski kompleks djeluje poput osiguraÄa Äija je funkcija poboljÅ”anje toÄnosti dekodiranja.The fidelity of protein biosynthesis is preserved by accurate aminoacylation of a specific transfer RNA (tRNA) with a cognate amino acid and the ribosomal decoding of each aminoacylated tRNA. Aminoacyl-tRNA synthetases (aaRS) catalyze the first reaction and are well known to interact with other cellular proteins. In the archaeon Methanothermo-bacter thermautotrophicus a complex is formed by the transient gathering of the arginyl- and seryl-tRNA synthetase (ArgRS and SerRS). Pull down and surface plasmon resonance experiments with truncated ArgRS variants showed that N-terminal part of ArgRS serves as the recognition platform for SerRS, with emphasis to the elements involved in tRNAArg recognition. Shortened variants delta89-ArgRS and deltaNtot-ArgRS show decreased ability for cognate tRNA binding and charging. Regarding the effect that reaction precursors may have on the stability of ArgRS:SerRS complex it is shown that serylation reaction precursors exert no influence. Furthermore, tRNASer is able to participate in ternary [SerRS:tRNASer]:ArgRS complex formation with the stability comparable to that of the binary SerRS:ArgRS assembly. In contrast, interaction of these proteins is susceptible to the addition of fully modified tRNAArg transcript which ultimately leads to dissociation of the complex. Overexpression of MttRNAArg in E. coli cells results with the production of three distinct molecular species which differ in the amount of added posttranscriptional modifications. Arginyl-tRNA synthetase investigated in this work aminoacylates such substrates with comparable efficacy. Interestingly, SerRS is able to inhibit arginylation of poorer substrates, i. e. less modified tRNAArg molecules. Elimination of the partly modified tRNAs from the translation process shows how this protein complex acts as a safeguarding switch improving decoding accuracy
Globalni utjecaj i posljedice sukoba Tito-Staljin. The Tito-Stalin Split 70 Years After, ed. Tvrtko Jakovina & Martin PreviÅ”iÄ, Zagreb ā Ljubljana: FF press ā Znanstvena založba Filozofske fakultete Univerze v Ljubljani 2020, 260 str.
Analysis of leadership styles in Croatia
During the last two decades, leadership has become the focus of intense interest and research by scientists and theorists. A large number of leadership models have been developed in order to define and enable a certain level of business flexibility that is crucial for survival in a new business environment characterized by frequent market changes, growing global competition and technology development together with demographic changes of employees. This paper aims to determine the dominant leadership style in organizations in Croatia. For the purpose of this paper, empirical research was conducted with the goal of defining the leadership styles of top and middle management of 205 active organizations in Croatia. The research was based on the leadership model developed and established by Rensis Likert. An analysis of leadership styles variables showed that there is a distinguished leadership style in organizations in Croatia. Furthermore, there is an empirically distinguished leadership style concerning the size of the organizations, ownership type and the branches of activity of the organizations in Croatia
- ā¦