Search PubMed⌕ Search

Biomedical subjects

L Bogorad

Publications and source records attributed to L Bogorad.

At least 145 records · Page 8Linked to original sources
PubMed1974

The polypeptide subunit structure of the DNA-dependent RNA polymerase of Zea mays chloroplasts.

Analysis of the maize chloroplast DNA-dependent RNA polymerase by electrophoresis on polyacrylamide gels that contain sodium dodecyl sulfate shows that the enzyme is multimeric. It contains at least two polypeptides of 180,000 and 140,000 daltons. Polypeptides of lower molecular mass that are associated with the enzyme at several stages of purification may also be subunits of the enzyme. Electrophoresis of a mixture of purified maize nuclear DNA-dependent RNA polymerase IIA and chloroplast polymerase on sodium dodecyl sulfate-polyacrylamide gels resolves the 160,000 dalton polypeptide of IIA from the 140,000 dalton polypeptide of the chloroplast enzyme, but does not resolve the 180,000 dalton components found in both enzymes. The polypeptides of less than 40,000 daltons in the highly purified maize nuclear IIA preparations are absent from preparations of purified maize chloroplast RNA polymerase.

Chloroplasts↗
PubMed1973

RNA polymerases of maize. Purification and molecular structure of DNA-dependent RNA polymerase II.

Nuclear DNA-dependent RNA polymerase II has been purified from leaves of Zea mays by a new procedure that improves enzyme stability and thus permits more manipulation during purification. The purification procedure includes a heating step, gel filtration on Sepharose 6B and 4B, and chromatography on DEAE- and DNA-celluloses. This method of purification yields an enzyme that exhibits maximal activity when denatured DNA is used as a template. Electrophoresis of highly purified enzyme on polyacrylamide gels containing sodium dodecyl sulfate indicates that maize RNA polymerase IIa is composed of several polypeptide subunits. The most highly purified preparations contain polypeptides with molecular weights of 200,000, 160,000, 35,000, 25,000, 20,000, and 17,000.

Chromatography↗
PubMed1973

Complementary chromatic adaptation in a filamentous blue-green alga.

Fluorescent and red light environments generate greatly different patterns of pigmentation and morphology in Fremyella diplosiphon. Most strikingly, red-illuminated cultures contain no measurable C-phycoerythrin and have a mean filament length about 10 times shorter than fluorescent-illuminated cultures. C-phycoerythrin behaves as a photoinducible constituent of this alga. Spectrophotometric and immunochemical procedures were devised so that C-phycoerythrin metabolism could be studied quantitatively with [(14)C]-phenylalanine pulse-chased cultures. Transfer of red-illuminated cultures to fluorescent light initiates C-phycoerythrin production by essentially de novo synthesis. C-phycoerythrin is not degraded to any significant extent in cultures continuously illuminated with fluorescent light. Transfer of fluorescent-illuminated cultures to red light causes an abrupt cessation of C-phycoerythrin synthesis. The C-phycoerythrin content of cultures adapting to red light decreases and subsequently becomes constant. Loss of C-phycoerythrin is not brought about by metabolic degradation, but rather by a decrease in mean filament length which is effected by transcellular breakage. In this experimental system, light influences intracellular C-phycoerythrin levels by regulating the rate of synthesis of the chromoprotein.

Adaptation, Physiological↗
PubMed1973

Effect of light on ribonucleic Acid metabolism in greening maize leaves.

The effect of illumination on the incorporation of labeled precursors into RNA of dark-grown maize (Zea mays) leaves was studied using either (32)P-phosphate or double labeling with (14)C- and (3)H-uridine. In the dark, label was preferentially incorporated into etioplast ribosomal RNAs. Incorporation into this fraction and into lower molecular weight fractions was strongly and preferentially stimulated by light during the first 2 hours of illumination. The effect persisted after illumination was terminated. The possibility that light-induced alterations in plastid ribosomal RNA metabolism may not be required for chlorophyll accumulation in maize is discussed.Sucrose density gradient analyses of ribosomes and of extracted RNA did not reveal light-induced incorporation of label into messenger-like RNA associated with polyribosomes during brief illumination. However, newly produced RNA which seems to be neither ribosomal RNA nor transfer RNA is detectable after illumination for 2.5 hours or longer.

Journal Article↗
PubMed1973

Steps in the acquisition of photosynthetic competence by plastids of maize.

Coupling factor particles are associated with membranes of maize etioplasts (Lockshin et al., 1971. Biochim. Biophys. Acta 226: 366-382). In addition, several, but not all, of the polypeptides found in the photosynthetic lamellae of maize chloroplasts are present in etioplasts.During the photoregulated maturation of chloroplasts from etioplasts, the membranes of the organelle acquire the capacity to carry on acid to base phosphorylation. The acquisition of this ability is closely correlated with the development of osmotic responsiveness and the appearance of a 46,000 dalton polypeptide in the membranes.

Journal Article↗
PubMed1972

Altered chlorplast ribosomal proteins associated with erythromycin-resistant mutants in two genetic systems of Chlamydomonas reinhardi.

The phenotype of several erythromycin-resistant mutants of Chlamydomonas reinhardi was further characterized in terms of the electrophoretic properties of their chloroplast ribosomal proteins. In mutant ery-M2d a single protein of the large (52 S) subunit has altered properties, which probably result from a change in its primary sequence. This mutation is inherited in a Meudelian manner. In mutant ery-U1a, which is inherited in a uniparental manner, a different single protein of the 52 S subunit is altered. This change might result from a change in either the primary sequence of the protein or in some form of secondary modification. These results indicate that these two distinct genetic systems must cooperate in the production of chloroplast ribosomes.

Centrifugation, Density Gradient↗
PubMed1971

Mendelian and uniparental alterations in erythromycin binding by plastid ribosomes.

Erythromycin binds specifically to the 52S subunit of the chloroplast ribosome of Chlamydomonas reinhardi. A number of erythromycin-resistant mutants whose ribosomes have lost their affinity for the antibiotic have been isolated, but the sedimentation properties of their ribosomes are indistinguishable from those of the wild-type strain. These mutants represent at least three genetic loci. Two of them show Mendelian inheritance, and one of them is inherited in a uniparental manner.

Binding Sites↗
PubMed1971

RNA polymerases of maize: partial purification and properties of the chloroplast enzyme.

A DNA-dependent RNA polymerase has been solubilized and partially purified from washed chloroplasts prepared from maize seedlings. The purified enzyme was completely dependent on added DNA after purification by phospho- or DEAE-cellulose chromatography. On glycerol density gradients, the enzyme ran ahead of a marker with a sedimentation constant of 18 S, indicating a molecular weight of 500,000 or more. The instability of the highly purified enzyme made intensive study difficult, but the properties of the enzyme purified by phosphocellulose chromatography are reported. Template specificity varied during purification but the activity was always higher with denatured than with native DNA and the preference for maize DNA over calf-thymus DNA increased during purification. The enzyme required magnesium for optimal activity, was inhibited by salt concentrations in excess of 0.1 M, and had a temperature optimum of 48 degrees C. The chloroplast enzyme differed from similar activities so far reported from maize or other sources, particularly in the high salt concentrations needed to elute it from phosphocellulose. The soluble, DNA-dependent enzyme was not inhibited by either alpha-amanitin or by rifamycin-SV under the assay conditions used.

Adenosine Monophosphate↗
PubMed1971

RNA polymerases of maize: nuclear RNA polymerases.

Two DNA-dependent RNA polymerases of nuclear origin have been purified from leaves of Zea mays. The two enzymes can be separated on DEAE-cellulose columns. Enzymes I and II are eluted with 0.08 and 0.20 M (NH(4))(2)SO(4), respectively. Both enzymes prefer maize nuclear DNA as a template; they are also more active in the presence of Mg(++) than Mn(++) and are inhibited by (NH(4))(2)-SO(4) or KCl. Neither enzyme is inhibited by rifamycin SV. Enzyme II is strongly inhibited by alpha-amanitin, whereas enzyme I is not significantly affected. Their ability to use native and denatured DNA as templates varies according to the extent and method of purification of the polymerase. Furthermore, enzyme II can be resolved by DEAE-chromatography or glycerol-gradient centrifugation into two components, one of which prefers native DNA, while the other prefers denatured DNA.

Ammonium Sulfate↗