Proteolysis in Euglena gracilis. IV. Proteolytic Activities During Light-induced Chloroplast Formation in Resting Cells1

Scheer, Angellka; Parthier, B.; Krauspe, R.

doi:10.1016/s0176-1617(86)80229-2

Cited by 2 publications

(1 citation statement)

References 20 publications

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“…The sediment was resuspended in 2 ml of Hepes buffer III (50 mM Hepes-KOH, pH 8.0; 330 mM sorbitol; 10 mM /?-mercaptoethanol; 50 gM each of the proteinase inhibitors, leupeptin and pepstatin A), according to Mishkind et al (1985) and Scheer et al (1986). The suspension was layered onto 2 ml of a cushion of 40% Percoll dissolved in the same buffer without mercaptoethanol but containing 0.4% bovine serum albumin (Grossman et al 1982).…”

Section: Cells Euglena Gracilis Zmentioning

confidence: 99%

In-vitro transport of chloroplast proteins in a homologousEuglena system with particular reference to plastid leucyl-tRNA synthetase

Reinbothe

Krauspe

Parthier

1990

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In-vitro translations of total or polyadenylated RNA from chemoorganotrophic and photoautotrophicEuglena gracilis showed no substantial differences in the polypeptide patterns of the two cell types. By contrast, the corresponding patterns of in-vivo labelling indicated that posttranscriptional control of abundant cellular proteins occurred in illuminated cells. This type of control was confirmed forEuglena chloroplast proteins of cytoplasmic origin. The posttranslational transport of in-vitro-formed polypeptides into homologous chloroplasts allowed the plastid-targeted proteins to be recognized. Estimations of the amounts of in-vitro-translated polypeptides showed that the mRNA levels for nuclearencoded chloroplast proteins were almost constant throughout chloroplast development inEuglena. The import of the in-vitro-translation products into the chloroplasts was demonstrated (i) by kinetic determination of radioactivity increasing inside and decreasing outside the organelles, (ii) by autoradiographic analysis of the transported translation products among two-dimensionally separated chloroplast proteins, and (iii) by autoradiographic estimation of the decrease in labelled polypeptides in the incubation medium. After 60 min of incubation in the presence of chloroplasts, about 20% of the in-vitro-labelled translation products, corresponding to 30 protein spots, were found to be redistributed into the organelles. Low-abundance chloroplast leucyl-tRNA synthetase (LeuRS) was detected immunologically among the in-vitro translation products as a precursor protein (pre-LeuRS) of 112 kilodaltons (kDa), which was transported into chloroplasts where it was present in the form of the 105-kDa mature enzyme. Processing of pre-LeuRS also seemed to occur using wheat-germ translation system; however, the mature enzyme was not sequestered intoEuglena chloroplasts. Our results indicate that a nuclear-encoded chloroplastic aminoacyl-tRNA synthetase, the product of a low-abundance mRNA, is transported into and processed in chloroplasts in vitro.

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Section: Cells Euglena Gracilis Zmentioning

confidence: 99%

In-vitro transport of chloroplast proteins in a homologousEuglena system with particular reference to plastid leucyl-tRNA synthetase

Reinbothe

Krauspe

Parthier

1990

Planta

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Proteolysis in Euglena gracilis

Krauspe

Scheer

Schaper

et al. 1986

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Endoproteolytic activities (EC 3.4.22. and 23.) of cell-free extracts of Euglena gracilis, measured by autolysis and azocaseinolysis, vary considerably during the culture growth cycle. They are high in the lag phase, drop sharply up to the mid-logarithmic phase, and then rise again reaching the initial high levels in the stationary phase. This pattern has been observed for both the soluble and the particulate proteolytic activities of four cell types differing with regard to the developmental state of the chloroplast: dark-grown, light-induced, and light-grown wild-type cells, as well as light-grown apoplastic W3BUL mutant cells, all on a glucose-based medium. Therefore, the activity of the main intracellular proteinases is neither directly nor indirectly light-regulated, but seems to be controlled by the availability of nutrients. Endogenous inhibitors of proteinases could not be detected. Cysteine proteinase activity has been found in the soluble and the particulate fractions, but aspartic proteinase activity in the latter ones only. Different cysteine proteinases may be present in the two fractions, during the different growth phases, and in the four cell types studied.

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Proteolysis in Euglena gracilis. IV. Proteolytic Activities During Light-induced Chloroplast Formation in Resting Cells1

Cited by 2 publications

References 20 publications

In-vitro transport of chloroplast proteins in a homologousEuglena system with particular reference to plastid leucyl-tRNA synthetase

In-vitro transport of chloroplast proteins in a homologousEuglena system with particular reference to plastid leucyl-tRNA synthetase

Proteolysis in Euglena gracilis

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