Biomedical subjects
L Giri
Publications and source records attributed to L Giri.
Purification of ribosomal proteins from Escherichia coli by cation exchange and reversed phase FPLC.
A complex mixture of 21 proteins from the 30S ribosomal subunit of Escherichia coli was fractionated on a cation-exchanger, then further separated on a C8 reversed-phase column. A set of 14 proteins were purified to homogeneity. The same protein mixture was also analysed on a C8 RPC column using a triethylamine phosphate (TEAP, pH2.2)/acetonitrile or a trifluoroacetic acid/acetonitrile solvent system which gave 11 and 8 purified proteins, respectively. Altogether, 16 out of 21 proteins from the 30S ribosomal subunit were purified.
Physical studies on assimilatory nitrate reductase from Chlorella vulgaris.
Assimilatory nitrate reductase (EC 1.6.6.1 NADH:nitrate oxidoreductase) from Chlorella vulgaris purified by affinity chromatography was found to be homogeneous as judged by electrophoresis on sodium dodecyl sulfate-polyacrylamide gel and by analytical ultracentrifugal techniques. The molecular weight of the intact enzyme and that of the enzyme dissociated in 6 M GuHCl, determined by sedimentation equilibrium studies, were 280,000 +/- 10,000 and 90,000 +/- 5,000, respectively. Comparable values were obtained using the S20,w value and the D20,w values in Svedberg's equation. The D20,w values were determined by laser light-scattering measurements. Active enzyme centrifugation showed that the monomer is an active species. A quantitative re-evaluation of the prosthetic groups present (FAD, heme, and molybdenum) was also made and was consistent with the conclusion that the active monomer contains three subunits as previously deduced by Solomonson et al. ((1975) J. Biol. Chem. 250, 4120). Electron micrographs showed images which corresponded to three subunits, supporting the data obtained by hydrodynamic studies. The enzyme is not cigar-shaped, as previously surmised, but has a roughly globular structure.
Shape of proteins S3 and S17 from the small subunit of Escherichia coli ribosome.
The shapes of proteins S3 and S17 purified from the 30 S subunit of Escherichia coli A19 were studied by hydrodynamic methods. The proteins have s020,w values of 2.1 +/- 0.1 S and 1.2 +/- 0.1 S and D020,w values of 7.4 +/- 0.5 . 10(-7) cm2/s and 11.4 +/- 0.6 . 10(-7) cm2/s. The respective molecular weights determined by sedimentation equilibrium are 25 800 +/- 500 and 9900 +/- 300. The intrinsic viscosity values for the two proteins are 5.8 +/- 0.3 ml/g and 4.2 +/- 0.2 ml/g. From these hydrodynamic parameters a slightly elongated shape for S3 and a globular shape for S17 have been concluded.
Shapes of proteins L1, L9, L25, and L30 from the 50S subunit of the Escherichia coli ribosome, determined by hydrodynamic studies.
Proteins L1, L9, L25, and L30, purified by a nondenaturing method from the 50S ribosomal subunit of Escherichia coli A19, have been characterized. The four proteins were studied under conditions which resemble those used for reconstitution experiments. These proteins have S020,W values of 2.0 S, 1.8 S, 1.8 S, and 1.0 S and D20,W values of 8.4 X 10(-7), 9.0 X 10(-7), 14.0 X 10(-7), and 15.0 X 10(-7) cm2/S. Apparent specific volumes at 20 degrees C are 0.738, 0.733, 0.700, and 0.735 mL/g for the four proteins. The respective molecular weights determined by sedimentation equilibrium are 25 000, 17 300, 12 000, and 6500. The intrinsic viscosity values for the four proteins are 4.0, 5.5, 3.6, and 3.2 mL/g. From these hydrodynamic parameters L1 and L9 appear to have globular or at most only slightly elongated shapes, whereas L25 and L30 appear to be definitely globular.
Hydrodynamic studies on the Escherichia coli 30S ribosomal subunits and 30S.IF-3 complex.
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Physical studies on proteins L3 and L24 from the 50 S subunit of the Escherichia coli ribosome.
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Shape of protein S5 from the 30 S subunit of Escherichia coli ribosome determined in two different ionic environments.
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The shape of proteins S15 and S18 from the small subunit of the Escherichia coli ribosome.
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Shape of protein L11 from the 50S ribosomal subunit of Escherichia coli.
Protein L11 from the 50S ribosomal subunit of Escherichia coli A19 was purified by a method using nondenaturing conditions. Its shape in solution was studied by hydrodynamic and low-angle x-ray scattering experiments. The results from both methods are in good agreement. In buffers similar to the ribosomal reconstitution buffer, the protein is monomeric at concentrations up to 3 mg/mL and has a molecular weight of 16 000-17 000. The protein molecule resembles a prolate ellipsoid with an axial ratio of 5-6:1 a radius of gyration of 34 A, and a maximal length of 150 A. From the low-angle x-ray diffraction data, a more refined model of the protein molecule has been constructed consisting of two ellipsoids joined by their long axes.
Hydrodynamic properties of protein S1 from Escherichia coli ribosome.
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Hydrodynamic studies on the Escherichia coli robosomal proteins S8 and L6, prepared by two different methods.
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Physical characteristics of protein-deficient derived from the 50S ribosomal subunit.
Sedimentation coefficients, diffusion coefficients, density increments, extinction coefficients, and molecular weights were determined for selected core particles from the 50S Escherichia coli ribosomal subunits. These core particles were found to be loosened structures containing less than half the protein present on the intact 50S subunits and totally lacking peptidyl transferase and polyphenylalanine synthesis activity unless reconstituted. The results of this study confirm that a loosening of the subunit takes place upon the removal of protein, but this loosening is not necessarily due to the loss of the protein.