Dissociation of the ribulosebisphosphate-carboxylase large-subunit binding protein into dissimilar subunits

ABSTRACT mRNA levels of several Crithidia fasciculata genes involved in DNA metabolism have previously been found to cycle as cells progress through the cell cycle. Octamer consensus sequences in the 5′ untranslated regions (5′ UTRs) of these transcripts were shown to be required for cycling of these mRNAs. The KAP3 gene encodes a kinetoplast histone H1-like DNA binding protein, and its mRNA levels cycle in parallel with those of the kinetoplast DNA topoisomerase (TOP2), dihydrofolate reductase-thymidylate synthase (DHFR-TS), and the large subunit of the nuclear single-stranded DNA binding protein (RPA1). KAP3 mRNA contains two octamer consensus sequences in its 3′ UTR but none in its 5′ UTR. Mutation of these octamer sequences was not sufficient to prevent cycling of a sequence-tagged KAP3 mRNA expressed from a plasmid. Mutation of an octamer sequence contained on the precursor transcript but not on the mRNA, in addition to mutation of the two octamer sequences in the 3′ UTR, was necessary to abolish cycling of the mRNA. The requirement for a sequence not present on the mature mRNA indicates that regulation of the mRNA levels by the octamer sequences occurs at or prior to splicing of the transcript. Incompletely processed RNAs containing octamer sequences were also found to accumulate during the cell cycle when the mRNA levels were lowest. These RNA species hybridize to both the KAP3 coding sequence and that of the downstream drug resistance gene, indicating a lack of processing within the intergenic region separating these genes. We propose a cell cycle-dependent interference in transcript processing mediated by octamer consensus sequences as a mechanism contributing to the cycling of such transcripts.

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Limitation of the Rate of Ribulosebisphosphate Carboxylase Activation by Carbamylation and Ribulosebisphosphate Carboxylase Activase Activity: Development and Tests of a Mechanistic Model

Functional Plant Biology ◽

10.1071/pp9960141 ◽

1996 ◽

Vol 23 (2) ◽

pp. 141 ◽

Cited By ~ 20

Author(s):

IE Woodrow ◽

ME Kelly ◽

KA Mott

Keyword(s):

Mechanistic Model ◽

Large Subunit ◽

Intercellular Co2 Concentration ◽

Rubisco Activase ◽

Photon Flux ◽

Photon Flux Density ◽

Bisphosphate Carboxylase ◽

Ribulosebisphosphate Carboxylase ◽

Kinetics Of ◽

Rubisco Activation

A mechanistically-based model of light-mediated activation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is developed. The model describes the kinetics of Rubisco activation following a relatively rapid increase in photon flux density (PPFD) from an initially low level. Underlying the model is the assumption that there are two slow processes that could potentially limit the rate of light-mediated Rubisco activation. These processes are the addition of the activator CO2 to the large subunit of Rubisco, which is accompanied by a conformational change in the enzyme (carbamylation), and activase-mediated removal of ribulose 1,5-bisphosphate from the inactive form of the enzyme. The contribution of these slow processes to the overall activation kinetics of Rubisco was resolved by measuring Rubisco activation in whole spinach leaves using non-steady-state CO2 exchange. It was found that when the change in PPFD was relatively small and a correspondingly small proportion of the Rubisco pool was activated, the kinetics of activation were highly sensitive to the intercellular CO2 concentration (ci). The apparent rate constant for activation under these conditions was found to be similar to that for the carbamylation of purified spinach Rubisco. When the change in PPFD and the proportion of Rubisco activated was relatively large, however, the kinetics of Rubisco activation were almost completely CO2 insensitive and were consistent with those of an enzyme-catalysed reaction. It is suggested that (1) CO2-insensitive activation reflects the operation of Rubisco activase and (2) the increasing CO2 sensitivity seen as the change in PPFD decreases reflects a transition to limitation by carbamylation.

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Comparison of the structure and function of ribulosebisphosphate carboxylase–oxygenase from a cold-hardy and nonhardy potato species

Canadian Journal of Biochemistry ◽

10.1139/o81-039 ◽

1981 ◽

Vol 59 (4) ◽

pp. 280-289 ◽

Cited By ~ 24

Author(s):

Norman P. A. Huner ◽

Jiwan P. Palta ◽

Paul H. Li ◽

John V. Carter

Keyword(s):

Large Subunit ◽

Structure And Function ◽

Sulfhydryl Groups ◽

Relative Mass ◽

Nitrobenzoic Acid ◽

Significant Difference ◽

Ribulosebisphosphate Carboxylase ◽

Cold Hardy ◽

And Function ◽

Kinetics Of

A comparison of ribulosebisphosphate carboxylase–oxygenase from the leaves of the non-acclimated, cold-hardy species, Solanum commersonii, and the nonacclimated, nonhardy species, Solanum tuberosum showed that this enzyme from the two species differed in structure and function. The results of sulfhydryl group titration with 5,5′-dithiobis(2-nitrobenzoic acid) indicated that the kinetics of titration and the number of accessible sulfhydryl groups in the native enzymes were different. After 30 min, the enzyme from the hardy species had 1.7 times fewer sulfhydryl groups titrated than that from the nonhardy species. In the presence of 1% (w/v) sodium dodecyl sulfate, the total number of sulfhydryl groups titratable with 5,5′-dithiobis-(2-nitrobenzoic acid) was the same for both species. However, this denaturant had a differential effect on the kinetics of titration with 5,5′-dithiobis(2-nitrobenzoic acid). Both enzymes had a native molecular weight of about 550 000. The quaternary structures of the two enzymes were similar with the presence of large and small subunits of 54 000 and 14 000, respectively. However, there was more polypeptide of 108 000 – 110 000 present in preparations of the enzyme from S. tuberosum than from S. commersonii. This polypeptide is an apparent dimer of the large subunit on a relative mass basis. The large subunit of the enzyme from S. tuberosum was more sensitive to the absence of reducing agent and was more sensitive to freezing and thawing than the large subunit of the enzyme from S. commersonii. Catalytic properties of both enzymes at 5 and 25 °C indicated no significant difference in the [Formula: see text] at either temperature. However, the Vmax at 5 °C for the enzyme from S. commersonii was 35% higher than that of the enzyme from S. tuberosum. In contrast, the Vmax at 25 °C for the enzyme of the hardy species was 250% lower than that of the enzyme from the nonhardy species.

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Partial amino acid sequence of the large subunit of ribulosebisphosphate carboxylase from barley

Carlsberg Research Communications ◽

10.1007/bf02906297 ◽

1979 ◽

Vol 44 (3) ◽

pp. 191-199 ◽

Cited By ~ 18

Author(s):

Carsten Poulsen ◽

Brian Martin ◽

Ib Svendsen

Keyword(s):

Amino Acid ◽

Amino Acid Sequence ◽

Large Subunit ◽

Partial Amino Acid Sequence ◽

Ribulosebisphosphate Carboxylase

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Stress induces the assembly of RNA granules in the chloroplast of Chlamydomonas reinhardtii

The Journal of Cell Biology ◽

10.1083/jcb.200805125 ◽

2008 ◽

Vol 182 (4) ◽

pp. 641-646 ◽

Cited By ~ 34

Author(s):

James Uniacke ◽

William Zerges

Keyword(s):

Oxidative Stress ◽

Chlamydomonas Reinhardtii ◽

Large Subunit ◽

Ribosomal Subunit ◽

Stress Granules ◽

Mrna Localization ◽

Messenger Rnas ◽

Rna Granules ◽

Cytoplasmic Rna ◽

Ribulosebisphosphate Carboxylase

Eukaryotic cells under stress repress translation and localize these messenger RNAs (mRNAs) to cytoplasmic RNA granules. We show that specific stress stimuli induce the assembly of RNA granules in an organelle with bacterial ancestry, the chloroplast of Chlamydomonas reinhardtii. These chloroplast stress granules (cpSGs) form during oxidative stress and disassemble during recovery from stress. Like mammalian stress granules, cpSGs contain poly(A)-binding protein and the small, but not the large, ribosomal subunit. In addition, mRNAs are in continuous flux between polysomes and cpSGs during stress. Localization of cpSGs within the pyrenoid reveals that this chloroplast compartment functions in this stress response. The large subunit of ribulosebisphosphate carboxylase/oxygenase also assembles into cpSGs and is known to bind mRNAs during oxidative stress, raising the possibility that it plays a role in cpSG assembly. This discovery within such an organelle suggests that mRNA localization to granules during stress is a more general phenomenon than currently realized.

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