PubMed Health⌕ Search

Biomedical subjects

R C Fuller

Publications and source records attributed to R C Fuller.

53 records · Page 3Linked to original sources
PubMed1969

Pteridines and the function of the photosynthetic reaction center.

The photoreduction and interaction with the photosynthetic "reaction center" of 2-amino,4-hydroxy-6-substituted pteridine indicates that these low-potential ( approximately -0.7 v), naturally occurring compounds play a primary role in photosynthetic electron transport. These unconjugated pteridines, which occur in association with the photosynthetic apparatus of green plants and photosynthetic bacteria, can be reduced by light in the presence of a bacterial chromatophore fraction from the dihydro form to the tetrahydro form. 6,7-Dimethyl-tetrahydropteridine readily reduces spinach ferredoxin. This compound also specifically interacts with reaction-center chlorophyll and bacteriochlorophyll and produces spectral shifts similar to those produced by light. It is proposed that the electron produced by excited-state chlorophyll is captured and separated by a pteridine at -0.67 v at the photosynthetic reaction center.

Chloroplasts↗
PubMed1967

Carotenoid biosynthesis in Rhodospirillum rubrum: effect of pteridine inhibitor.

A known inhibitor of pteridine utilization (4-phenoxy,2,6-diamino pyridine) blocks the synthesis of colored carotenoids in the photosynthetic bacterium Rhodospirillum rubrum. In many ways the effect is similar to the inhibition of the synthesis of colored carotenoids by diphenylamine. This inhibition is probably independent of other effects of pteridine on photosynthetic electron transport since it is not as readily reversible as the total inhibition of photosynthetic activity by pteridine analogs.

Carotenoids↗
PubMed1967

Photosynthesis in Rhodospirillum rubrum. I. Autotrophic carbon dioxide fixation.

The incorporation and distribution of activity from (14)CO(2) was investigated under autotrophic conditions in the facultative photoautotroph, Rhodospirillum rubrum, with cells cultured on hydrogen, carbon dioxide, and ammonium sulfate. In 1 second (14)CO(2) fixation experiments essentially all of the activity was found in 3-phosphoglyceric acid: plotted against time percent incorporation into phosphate esters has a strikingly negative slope. These results suggest that under autotrophic conditions the reductive pentose phosphate cycle or the key reactions of the cycle play a major role in carbon metabolism in this photosynthetic bacterium. Incorporation into amino acids and into intermediates of the tricarboxylic acid cycle was quite low.

Carbon↗
PubMed1967

Photosynthesis in Rhodospirillum rubrum. II. Photoheterotrophic carbon dioxide fixation.

The contribution of the reductive pentose phosphate cycle to the photometabolism of carbon dioxide and to carbon metabolism in Rhodospirillum rubrum grown photoheterotrophically with l-malate as the carbon source is nil, unlike autotrophically grown R. rubrum. Glycolic acid appears to be the first stable product of CO(2) fixation in R. rubrum cultured photoheterotrophically on l-malate. The results obtained in (14)CO(2) fixation experiments suggest that the photometabolism of CO(2) through glycolate into malate is a major pathway of CO(2) fixation in such cells. However, l-malate was a much more efficient precursor of phosphate esters, and of glutamic acid, than was carbon dioxide; l-malate is therefore, in this case, a far more important source of cell carbon than is carbon dioxide. The products of the light-dependent incorporation of CO(2) and of acetate were investigated in R. rubrum grown photoheterotrophically on acetate. Carboxylation reactions and the reductive pentose phosphate cycle are apparently of greater significance in the photometabolism of acetate heterotrophs than in malate heterotrophs; the photometabolism of the acetate photoheterotrophs seems to be intermediate between the photoheterotrophy of malate heterotrophs and strict autotrophy.

Carbon↗
PubMed1967

Photosynthesis in Rhodospirillum rubrum. 3. Metabolic control of reductive pentose phosphate and tricarboxylic acid cycle enzymes.

Enzymes of the reductive pentose phosphate cycle including ribulose-diphosphate carboxylase, ribulose-5-phosphate kinase, ribose-5-phosphate isomerase, aldolase, glyceraldehyde-3-phosphate dehydrogenase and alkaline fructose-1,6-diphos-phatase were shown to be present in autotrophically grown Rhodospirillum rubrum. Enzyme levels were measured in this organism grown photo- and dark heterotrophically as well. Several, but not all, of these enzymes appeared to be under metabolic control, mediated by exogenous carbon and nitrogen compounds. Light had no effect on the presence or levels of any of these enzymes in this photosynthetic bacterium. The enzymes of the tricarboxylic acid cycle and enolase were shown to be present in R. rubrum cultured aerobically, autotrophically, or photoheterotrophically, both in cultures evolving hydrogen and under conditions where hydrogen evolution is not observed. Light had no clearly demonstrable effect on the presence or levels of any of these enzymes.

Alkaline Phosphatase↗
PubMed1966

Photosynthetic Apparatus in the Green Bacterium Chloropseudomonas ethylicum.

Holt, Stanley C. (Dartmouth Medical School, Hanover, N.H.), S. F. Conti, and R. C. Fuller. Photosynthetic apparatus in the green bacterium Chloro-pseudomonas ethylicum. J. Bacteriol. 91:311-323. 1966.-When cells of Chloro-pseudomonas ethylicum were broken by ballistic disruption and examined by electron microscopy, vesicles 1,300 to 1,500 A long and 300 to 500 A wide were found to rim the periphery of the cell. Examination of these vesicles obtained by disruption with a French pressure cell and purified by density gradient centrifugation revealed inter-connections between the vesicles. During sonic and Mickle disruption of the cells, chlorophyll was released at a lower rate than soluble cytoplasmic components, but faster than the membrane-bound enzyme succinic dehydrogenase. Unlike the situation that exists in the purple photosynthetic bacteria, it appears that the chlorophyll in the green bacteria is contained as part of a structure which may be differentiated both structurally and functionally from the bacterial cytoplasmic membrane.

Journal Article↗
PubMed1966

Effect of light intensity on the formation of the photochemical apparatus in the green bacterium Chloropseudomonas ethylicum.

Holt, Stanley C. (Dartmouth Medical School, Hanover, N.H.), S. F. Conti, and R. C. Fuller. Effect of light intensity on the formation of the photochemical apparatus in the green bacterium Chloropseudomonas ethylicum. J. Bacteriol. 91:349-355. 1966.-When the green bacterium Chloropseudomonas ethylicum was grown at various light intensities, the formation of the photosynthetic vesicles was found to be an inverse function of the light intensity at which the cells were grown. The specific chlorophyll content of isolated vesicles varied as the light intensity was changed over a wide range. Thus, the regulation of chlorophyll content in C. ethylicum in response to a change in light intensity is achieved both by a change in the number of vesicles that are formed and by a change in the specific chlorophyll content of these vesicles.

Bacteria↗
PubMed1965

Alternative forms of triosephosphate dehydrogenase in Chromatium.

Triosephosphate dehydrogenase was purified extensively from the obligately phototrophic bacterium Chromatium. Enzyme prepared from photolithotrophically grown cells differed in several properties from enzyme prepared from photoorganotrophically grown cells. Either form of the enzyme could be transformed in vitro to the other by mild oxidation or reduction, which effected both Michaelis constants and reactive -SH contents of the proteins.

Chemical Precipitation↗
PubMedDate not supplied

Microbial inclusions with special reference to PHA inclusions and intracellular boundary envelopes.

Polyhydroxyalkanoates (PHAs), in the form of metabolic storage reserves, are assembled in intracellular cytoplasmic inclusions, often called granules. This review discusses both the structure and function of this assembly. In addition an overview of other microbial cellular inclusions is presented. This is not a compilation of all such structures but a description of those that are similar in many ways to either the structure or function of the PHA inclusions and are made up of monolayer envelopes and their storage compounds. Not unique, such inclusions provide many similar examples which, in turn, provide useful analogies to the PHA inclusions. A study of the PHA inclusions has been carried out in a comparative electron microscope examination and by protein analysis of a number of organisms and E. coli transformants.

Bacteria↗