Different oligomeric properties and stability of highly homologous A1 and proto-oncogenic A2 variants of mammalian translation elongation factor eEF1.

Translation elongation factor 1A (eEF1A) directs aminoacyl-tRNA to the A site of 80S ribosomes. In addition, more than 97% homologous variants of eEF1A, A1 and A2, whose expression in different tissues is mutually exclusive, may fulfill a number of independent moonlighting functions in the cell; for instance, the unusual appearance of A2 in an A1-expressing tissue was recently linked to the induction of carcinogenesis. The structural background explaining the different functional performance of the highly homologous proteins is unclear. Here, the main difference in the structural properties of these proteins was revealed to be the improved ability of A1 to self-associate, as demonstrated by synchrotron small-angle X-ray scattering (SAXS) and analytical ultracentrifugation. Besides, the SAXS measurements at different urea concentrations revealed the low resistance of the A1 protein to urea. Titration of the proteins by hydrophobic dye 8-anilino-1-naphthalenesulfonate showed that the A1 isoform is more hydrophobic than A2. As the different association properties, lipophilicity, and stability of the highly similar eEF1A variants did not influence considerably their translation functions, at least in vitro, we suggest this difference may indicate a structural background for isoform-specific moonlighting roles.

Formation of amyloid-like fibrils by Y-box binding protein 1 (YB-1) is mediated by its cold shock domain and modulated by disordered terminal domains.

YB-1, a multifunctional DNA- and RNA-binding nucleocytoplasmic protein, is involved in the majority of DNA- and mRNA-dependent events in the cell. It consists of three structurally different domains: its central cold shock domain has the structure of a ß-barrel, while the flanking domains are predicted to be intrinsically disordered. Recently, we showed that YB-1 is capable of forming elongated fibrils under high ionic strength conditions. Here we report that it is the cold shock domain that is responsible for formation of YB-1 fibrils, while the terminal domains differentially modulate this process depending on salt conditions. We demonstrate that YB-1 fibrils have amyloid-like features, including affinity for specific dyes and a typical X-ray diffraction pattern, and that in contrast to most of amyloids, they disassemble under nearly physiological conditions.

Analysis of micro- and nano-structures of the corneal surface of Drosophila and its mutants by atomic force microscopy and optical diffraction.

Drosophila melanogaster is a model organism instrumental for numerous biological studies. The compound eye of this insect consists of some eight hundred individual ommatidia or facets, ca. 15 µm in cross-section. Each ommatidium contains eighteen cells including four cone cells secreting the lens material (cornea). High-resolution imaging of the cornea of different insects has demonstrated that each lens is covered by the nipple arrays--small outgrowths of ca. 200 nm in diameter. Here we for the first time utilize atomic force microscopy (AFM) to investigate nipple arrays of the Drosophila lens, achieving an unprecedented visualization of the architecture of these nanostructures. We find by Fourier analysis that the nipple arrays of Drosophila are disordered, and that the seemingly ordered appearance is a consequence of dense packing of the nipples. In contrast, Fourier analysis confirms the visibly ordered nature of the eye microstructures--the individual lenses. This is different in the frizzled mutants of Drosophila, where both Fourier analysis and optical imaging detect disorder in lens packing. AFM reveals intercalations of the lens material between individual lenses in frizzled mutants, providing explanation for this disorder. In contrast, nanostructures of the mutant lens show the same organization as in wild-type flies. Thus, frizzled mutants display abnormal organization of the corneal micro-, but not nano-structures. At the same time, nipples of the mutant flies are shorter than those of the wild-type. We also analyze corneal surface of glossy-appearing eyes overexpressing Wingless--the lipoprotein ligand of Frizzled receptors, and find the catastrophic aberration in nipple arrays, providing experimental evidence in favor of the major anti-reflective function of these insect eye nanostructures. The combination of the easily tractable genetic model organism and robust AFM analysis represents a novel methodology to analyze development and architecture of these surface formations.