The conformational stability of ribosomal proteins L7 and L12 from E. coli. I. Circular dichroism study of the changes induced by ionic strength and solvents.
Explore the source record for details and available documents.
Circular Dichroism↗
Biomedical subjects
M Boublik
Publications and source records attributed to M Boublik.
The effect of various nucleotides on the helical nature of a ribosomal protein(s) from Escherichia coli.
In the presence of GTP or GDP, there is a decrease in the circular dichroic absorption of ribosomal proteins L(7) and L(12) at 221-222 nm, suggesting that these nucleotides influence the helical content of these proteins.
Adenosine Triphosphate↗
Proton magnetic resonance ttudies of the interactions of histones F1 and F2B with DNA.
Explore the source record for details and available documents.
Animals↗
Visualization of a ternary complex of the Escherichia coli Phe-tRNA(Phe) and Tu.GTP from Thermus thermophilus by scanning transmission electron microscopy.
Scanning transmission electron microscopy (STEM) was used to visualize formation of a ternary complex between the T. thermophilus elongation factor (EF) Tu.GTP and the Escherichia coli Phe-tRNA(Phe) labeled with an undecagold (Au11) cluster at minor nucleotide 3-(3-amino-3-carboxypropyl) uridine at position 47. The ternary complex was further characterized by the molecular mass and radius of gyration calculated from the mass distribution within the individual particles. Under conditions used for STEM imaging, the ternary complex is formed between Au11-labeled Phe-tRNA(Phe) and Tu.GTP in a yield up to 25%. The stoichiometry of EF-Tu.GTP to aminoacyl-tRNA (aa-tRNA) in the EF-Tu.GTP.aa-tRNA complex is 1:1, in agreement with the established view of the protein biosynthesis mechanism. The ternary complex is also formed, although to a lower extent, with GTP analogues (GMPPCP and GMPPNP, respectively), but not with Tu.GDP and nonaminoacylated tRNA(Phe) with Tu.GTP.
Escherichia coli↗
Heterogeneity of Escherichia coli ribosomes established by scanning transmission electron microscopy.
Quantitative mass image analysis of Escherichia coli ribosomal particles by scanning transmission electron microscopy (STEM) provided direct evidence that presumably homogeneous preparations of ribosomes are, in reality, populations of heterogeneous particles. Variations in composition, relative molecular mass (Mr) and shape were observed both in the monosomes and in the ribosomal subunits. None of these changes can be resolved visually; they can be evaluated only by computer processing. The variations in relative mass and shape monitored by values of radius of gyration (RG) were attributed to the loss of ribosomal proteins and/or factors and correlated with the changes in ribosome composition and biological activity. The highest activity was found in monosomes prepared from the standard 0.5 M NH4Cl wash. With increasing concentrations (up to 1.5 M) of NH4Cl in the wash buffer the activity decreased slowly, then dropped rapidly to about half in 2 M NH4Cl. The most striking effects were observed in ribosomal particles washed with 0.1 M NH4Cl. The 70S monosomes and the 30S subunits attained maximum Mr and RG values (2660 kDa and 76 A, and 990 kDa and 75 A, respectively), which were greater than the theoretical values, while the activity was minimal (approximately 12%). The Mr and RG parameters of the 50S subunits remained uneffected by the NH4Cl washes (approximately 1600 kDa and 68 A).
Escherichia coli↗
Image analysis of Artemia salina ribosomes by scanning transmission electron microscopy.
A dedicated scanning transmission electron microscope (STEM) at Brookhaven National Laboratory was used to visualize unstained freeze-dried ribosomal particles under conditions which considerably reduce the specimen distortion inherent in the heavy metal staining and air-drying preparative steps used in routine transmission electron microscopy (TEM). From high-resolution STEM images it is possible to determine molecular mass and the mass distribution within individual ribosomal particles and perform statistical evaluation of the data. Analysis of digitized STEM images of Artemia salina ribosomes provided evidence that a standard preparation of these eukaryotic ribosomes consists of a population of heterogenous particles. Because of the integrity of rRNAs established by agarose gel electrophoresis, variations in the composition and structure of the 80S monosomes and the large (60S) and small (40S) ribosomal subunits, as monitored by their mass, were attributed to the loss of ribosomal proteins, from the large subunits in particular. These results are relevant not only to the degree of ribosomal biological activity, but should also be taken into consideration for particle selection in the reconstruction of the "native" eukaryotic ribosome 3-D model.
Animals↗