A study of the water-soluble proteins of spinach beet chloroplasts with particular reference to fraction I protein

Abstract. Chloroplasts from leaves of plants which had been grown in the dark, and then illuminated for 12 hours were isolated, and allowed to incorporate 14C-leucine into protein, and the products of this incorporation were studied. Lamellar It has been reported that chloroplasts have the materials necessary for genetic autonomy. They contain ribosormes which would be necessary to convert the information in their DNA into proteins (8). A previous report from this laboratory showed that ch'loroplasts, in the crude chi4oroplast preparation tunder investigation, were responsible for the amino acid incorporation into protein that was observed in vitro (17). Amino acid incorporation into protein by chilorolplasts ha's been reported from a number of laboratories, as reviewed in the first publication in this series (17). The present work reports further studies of the system described previously, and was carried o-ut to find out the nature of the prodtucts formed. Materials and MethodsPlant Material. Chloroplasts of Phaseolus vulgaris L. var. Black Valentine were obtained from primary leaves as already described (17). Leaves were obtained froim plants grown in the dark for 6 days, and then illuminated with white light for 0.5 day.

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 96%

In vitro Protein Synthesis by Plastids of Phaseolus vulgaris. III. Formation of Lamellar and Soluble Chloroplast Protein

Margulies

Parenti

1968

“…16), RuDP carboxylase protein (9), and fraction I protein (9, 10), in response to leaf development and light, and relatively little on the fate of the enzyme after its synthesis. Fraction I protein and RuDP carboxylase are very probably identical (9,14,15,18,19). RuDP carboxylase activity and fraction I protein decrease during senescence of tobacco (1,8) and Perilla (7) leaves, but it is not known whether the enzyme is controlled by a turnover system or is degraded without simultaneous synthesis.…”

Section: Introductionmentioning

confidence: 95%

Evidence for Lack of Turnover of Ribulose 1,5-Diphosphate Carboxylase in Barley Leaves

Peterson¹,

Kleinkopf²,

Huffaker³

1973

Turnover of ribulose 1, 5-diphosphate carboxylase in barley leaves (Hordeum vulgare L.) was followed over time in light and dark. The enzyme was degraded in prolonged darkness and was resynthesized after the plants were returned to light. Labeling with 14C showed that simultaneous synthesis and degradation (turnover) did not occur in light. In contrast, the remaining soluble protein was turned over rapidly in light. Although ribulose 1, 5-diP carboxylase can be both degraded and synthesized, these processes seem not to occur simultaneously, but can be induced independently by changing environmental conditions. Much information is available on the increase of RuDPI carboxylase activity (6, 3, 9, 12, 13. 16), RuDP carboxylase protein (9), and fraction I protein (9, 10), in response to leaf development and light, and relatively little on the fate of the enzyme after its synthesis. Fraction I protein and RuDP carboxylase are very probably identical (9,14,15,18,19). RuDP carboxylase activity and fraction I protein decrease during senescence of tobacco (1,8) and Perilla (7) leaves, but it is not known whether the enzyme is controlled by a turnover system or is degraded without simultaneous synthesis.Since RuDP carboxylase protein makes up a large percentage of the total soluble protein of many plant leaves, it can be considered to be a major component of storage proteins (9, 14) as well as a major catalyst of CO2 fixation. A study was therefore done to determine whether RuDP carboxylase is controlled by a turnover system in barley leaves. MATERIALS AND METHODSPlant Materials. Hordeumn vulgar-e L. var. Numar was grown in vermiculite in 24-cm plastic pots or 28-X 33-cm plastic pans. Moisture was supplied by cotton wicks connecting the vermiculite to a full strength nutrient supply (9). The seedlings were grown for 6 days in either complete darkness or in continuous light (21,000 lux) at 27 C and 55% relative humidity. Plant Treatments. Loss of RuDP carboxylase from barley seedlings was followed in both darkness and continuous light. Six-day-old light-grown seedlings were placed in darkness, and the level of the enzyme was assayed every 6 hr for 72 hr. The seedlings were then returned to light, where the enzymatic assays were continued.'Abbreviation: RuDP: ribulose 1.5-diphosphate. This report defines turnover as simultaneous synthesis and degradation of protein. To determine whether RuDP carboxylase was being turned over while plants were in continuous light, RuDP carboxylase protein was labeled with "C by introducing CO2 when the leaves were rapidly synthesizing the enzyme (6, 9, 13). Six-day-old dark-grown barley seedlings were given 12 hr of light and then placed in a gas-tight chamber at 27 C under light (16,000 lux) and treated with 2 mc of "CO2. Continuous monitoring showed that at the end of 6 hr, about 80% of the "CO2 had been removed from the atmosphere of the chamber by the seedlings. At that point the plants were removed from the chamber and placed in continuous light (21,000 lux) at 27 C and 55% rel...

“…Table VIII shows that the albino mutant of barley does not have RuDP carboxylase activity. This enzyme is identical with the Fraction I protein of the chloroplast (22). This mutant, however, exhibits photocontrolled unrolling response in the same degree as the wild type, and leucine incorporation into the supernatant protein of the albino leaves is promoted by red light although to a somewhat lesser extent than in the wild type.…”

Section: Resultsmentioning

confidence: 82%

Phytochrome-controlled Leaf Unrolling and Protein Synthesis

Kang

1971

In the primary leaf sections of etiolated wheat (Triticum aestivum L.) seedlings, red light-induced unrolling is accompanied by an increase in incorporation of '4C-leucine into protein. By differential centrifugation, the unrolling response was found to be closely related to incorporation of the amino acid into the supernatant fraction (105,000g). Cycloheximide and chloramphenicol inhibit both leaf unrolling and synthesis of the supernatant protein, although chloramphenicol exerts its effect more strongly on the fraction which presumably contains the plastids. In a barley (Hordeum vulgare L.) albino mutant completely devoid of ribulose diphosphate carboxylase activity, only incorporation of 14C-leucine into the supernatant fraction is substantially promoted by red light. This mutant exhibits the photoresponse of leaf unrolling.Both unrolling and increased incorporation of '4C-leucine induced by red light are prevented by indoleacetic and abscisic acids. Kinetin promotes leucine incorporation into protein and can induce unrolling in complete darkness. Protein synthesis is still promoted by red light when unrolling is almost completely inhibited by an osmoticum. It is suggested that the action of red light on leaf unrolling is dependent on synthesis of a soluble protein in the tissue.The primary leaf of dark-grown grass seedlings unrolls after a brief exposure to red light, and a far red irradiation given after the irradiation with red light prevents this response, showing that unrolling is controlled by phytochrome (29). Exposure of etiolated leaves to light also results in a subsequent development of their plastid protein (7,13,21). There is evidence that phytochrome is involved in this process, too (9,11). In this paper, experiments on the action of red light on synthesis of various leaf protein fractions in segments from etiolated wheat leaves will be described, and the significance of a certain fraction, which is not bound to organelles, with regard to the leaf unrolling response will be discussed. were cut under dim green light from the primary leaf of 6-dayold seedlings, beginning 6 mm from the top. Kernels of an albino mutant (60-205A) as well as the wild type of barley (Hordeum vulgare L.) were germinated and grown, and leaf segments were isolated as described previously. The mutant was developed spontaneously after crossing cvs. Liberty and Kindred by Dr. J. E. Grafius, Department of Crop Science, Michigan State University. MATERIALS AND METHODS WheatRed light treatment was given by exposing the excised segments to light (intensity of 250 ergs/cm' * sec) from a fluorescent lamp wrapped with red cellophane.Ten leaf sections were floated in 2 ml of distilled water with test substances in a Petri dish (1 X 5 cm), except in the experiments with phenolic compounds, where a buffered solution was used. Leaf unrolling was measured by shadowgraphing the sections at the end of the incubation period and expressing the degree of unrolling in terms of the width of the sections.For labeling experiments 30 leaf...