Electron image analysis of ribosomal subunits from Thermus aquaticus

Inflammatory Thermophilic Fungi are Used in Biotechnology Applications

Thermophilic microorganisms which can colonize at extreme ecological niches are known as extremophiles. Because of their capacity to withstand high temperatures, enzymes from these organisms are relatively heat stable. The versatile enzyme properties of these organisms make them excellent candidates in biotechnology. In general, fungi have been widely used for the production of proteins and enzymes, since they can grow rapidly in a low cost media and they secrete proteins into the extra-cellular medium. Recently, these organisms have also been used in large scale fermentation as host for the expression of heterologous proteins in industrial applications. However, little is known about the regulation and genetic manipulations of these fungi. We have previously shown the regulation of gene expression in a thermophilic fungus, Thermyces lanuginosus, using an inducible invertase system. The aim of this review is to elucidate the recent advances of thermophilic fungi, and their implications in industrial applications are discussed.

UV-induced crosslinks in the 16S rRNAs of Escherichia coli, Bacillus subtilis and Thermus aquaticus and their implications for ribosome structure and photochemistry

Sixteen long-range crosslinks are induced in Escherichia coli 16S rRNA by far-UV irradiation. Crosslinking patterns in two other organisms, Bacillus subtilis and Thermus aquaticus, were investigated to determine if the number and location of crosslinks in E.coli occur because of unusually photoreactive nucleotides at particular locations in the rRNA sequence. Thirteen long-range crosslinks in B.subtilis and 15 long-range crosslinks in T.aquaticus were detected by gel electrophoresis and 10 crosslinks in each organism were identified completely by reverse transcription analysis. Of the 10 identified crosslinks in B.subtilis, eight correspond exactly to E.coli crosslinks and two crosslinks are formed close to sites of crosslinks in E.coli. Of the 10 identified crosslinks in T.aquaticus, five correspond exactly to E.coli crosslinks, three are formed close to E.coli crosslinking sites, one crosslink corresponds to a UV laser irradiation-induced crosslink in E.coli and the last is not seen in E.coli. The overall similarity of crosslink positions in the three organisms suggests that the crosslinks arise from tertiary interactions that are highly conserved but with differences in detail in some regions.

Characterization of functionally active subribosomal particles from Thermus aquaticus

Peptidyl transferase activity of Thermus aquaticus ribosomes is resistant to the removal of a significant number of ribosomal proteins by protease digestion, SDS, and phenol extraction. To define the upper limit for the number of macromolecular components required for peptidyl transferase, particles obtained by extraction of T. aquaticus large ribosomal subunits were isolated and their RNA and protein composition was characterized. Active subribosomal particles contained both 23S and 5S rRNA associated with notable amounts of eight ribosomal proteins. N-terminal sequencing of the proteins identified them as L2, L3, L13, L15, L17, L18, L21, and L22. Ribosomal protein L4, which previously was thought to be essential for the reconstitution of particles active in peptide bond formation, was not found. These findings, together with the results of previous reconstitution experiments, reduce the number of possible essential macromolecular components of the peptidyl transferase center to 23S rRNA and ribosomal proteins L2 and L3. Complete removal of ribosomal proteins from T. aquaticus rRNA resulted in loss of tertiary folding of the particles and inactivation of peptidyl transferase. The accessibility of proteins in active subribosomal particles to proteinase hydrolysis was increased significantly after RNase treatment. These results and the observation that 50S ribosomal subunits exhibited much higher resistance to SDS extraction than 30S subunits are compatible with a proposed structural organization of the 50S subunit involving an RNA "cage" surrounding a core of a subset of ribosomal proteins.