Structure of ribosomes from Thermomyces lanuginosus by electron microscopy and image processing

Cloning and expression of kinesins from the thermophilic fungus Thermomyces lanuginosus

The motor domain regions of three novel members of the kinesin superfamily TLKIF1, TLKIFC, and TLBIMC were identified in a thermophilic fungus Thermomyces lanuginosus. Based on sequence similarity, they were classified as members of the known kinesin families Unc104/KIF1, KAR3, and BIMC. TLKIF1 was subsequently expressed in Escherichia coli. The expression level was high, and the protein was mostly soluble, easy to purify, and enzymatically active. TLKIF1 is a monomeric kinesin motor, which in a gliding motility assay displays a robust plus-directed microtubule movement up to 2 microm/s. The discovery of TLKIF1 also demonstrates that a family of kinesin motors not previously found in fungi may in fact be used in this group of organisms.

Ribosomal proteins of Thermomyces lanuginosus--characterisation by two-dimensional gel electrophoresis and differential disassembly

One- and two-dimensional gel electrophoresis were employed to characterise the proteins derived from the ribosomes of the thermophilic fungus Thermomyces lanuginosus. Approximately 32 (29 basic and 3 acidic) and 45 (43 basic and 2 acidic) protein spots were resolved from Th. lanuginosus small and large ribosomal subunits, respectively. The molecular weight of the small subunit proteins ranged from 9,800-36,000 Da with a number average molecular weight of 20,300 Da. The molecular weight range for the large subunit proteins was 12,000-48,500 Da with a number average molecular weight of 25,900 Da. Most proteins appeared to be present in unimolar amounts. These data are comparable with but not identical to those from other eukaryotic ribosomes. The sensitivities of the ribosomal proteins to increasing concentrations of NH4Cl were also evaluated by two-dimensional gel electrophoresis. Most ribosomal proteins were gradually released over a wide range of salt concentrations but some were preferentially enriched in one or two salt conditions.

Electron microscopical projections of the large ribosomal subunit from Thermomyces lanuginosus

Multivariate statistical analysis and hierarchical ascendant classification have been used to construct averages of two fundamental electron microscopical views of large ribosomal subunits from the thermophilic fungus Thermomyces lanuginosus. The first was roughly pentagonal in shape and corresponded to the canonical crown view seen in images of large subunits from prokaryotic species. The second and more prevalent projection was elliptical in shape, and by matching protuberances could be interpreted as the complex rotated from the crown orientation. Because of its ubiquity and consistency, this elongated view could potentially serve as the standard for structural comparisons of the large ribosomal subunit from eukaryotic organisms, and as the basis for a three-dimensional reconstruction.

Characteristic electron microscopical projections of the small ribosomal subunit from Thermomyces lanuginosus

Multivariate statistical analysis and hierarchical ascendant classification techniques have been used to sort electron images of small ribosomal subunits from the thermophilic fungus Thermomyces lanuginosus into their characteristic views. Three predominant modes of adsorption to the support were elucidated: right-lateral, left-lateral and asymmetric, showing reproducible detail approaching 1.8 nm resolution. The projections of the fungal complexes appeared almost identical to those of HeLa cells, rat liver and rabbit reticulocytes studied previously in this manner. This result contrasts with the greater variation in fine structural features observed between ribosomal subunits from different prokaryotic species.

Electron image analysis of ribosomal subunits from Thermus aquaticus

Electron micrographs of ribosomal subunits from the thermophilic bacterium Thermus aquaticus were analysed using multivariate statistical analysis and characteristic views constructed to reproducible spatial resolutions ranging from 1.9 to 3.6 nm. These views were comparable to morphological classes of Escherichia coli ribosomal subunits, albeit with differences in fine features also found in archaebacterial ribosomes.

Covering events in eigenimages of biomolecules

Multivariate statistical analysis of a large set of micrographs of biological macromolecules involves the computation of eigenimages representing principal features, on the basis of which similar views of the complexes can be grouped. It is not generally clear what these eigenimages represent physically and which ones should be used in the classification process. In this paper, hierarchical maximum entropy discretisation and event covering are used to (1) detect statistically significant relationships in the eigenimages, (2) select the most relevant eigenimages for classifying biomolecular projections, and (3) build a prototype of the biomolecular complex under study.