Sequestration of Pea Reserve Proteins by Rough Microsomes

Hurkman, William J.; Beevers, Leonard

doi:10.1104/pp.69.6.1414

Cited by 16 publications

(6 citation statements)

References 21 publications

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“…In addition, the processing of band IV is much slower than of the other precursor proteins; the processing of the vicilin precursor in peas is also much slower (9 (7,19,27). Furthermore, the small decrease of Mr was also likely not due to the cleavage of a signal peptide during or after post-translational transport over membranes as reported for some enzymes (10,18), because the precursor protein is already sequestered within the rough endoplasmic reticulum (19,20). A small decreaseof Mr is also reported as a last processing step in the synthesis of storage proteins in other species (3,8,24 (Fig.…”

Section: Discussionmentioning

confidence: 73%

Biosynthesis of Storage Proteins in Ripening Agrostemma githago L. Seeds

Klerk

1984

Plant Physiol.

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The synthesis of storage proteins in ripening Agrostemma githago seeds was studied by in vivo pulse and pulse-chase experiments with labeled amino acids and labeled glucosamine. It was found that storage proteins were not synthesized directly, but via cleavage of several lrge precursor proteins. Two disulfide-linked proteins of38 and 25 kilodaltons were synthesized via a single large precursor protein. This precwusor protein contained internal disulfide bridges, at least one of which is involved in holding the subunit structre together following cleavage of the precursor. A similar mode of biosynthesis was noted for two other disulfide-linked proteins of 36 and 22 kilodaltons. The half-life of the precursors was about 2 hours. This mode of processing is a to the synthesis of legumin in legumes and globulin in oats. A third pair of disulfide-bonded proteins (41 and 23 kilodaltons) was synthesized from a precursor protein in several steps. These included a legumin-lke cleavage, whereafter the subunits remained disu}fide-bonded. Then, from the largest subunit, a part was cleaved off, probably a storage protein of 17 kilodaltons. This 17-kilUlton protein was not disulie-bonded to the 41 and 23-kihlodton complex. The first processing step was fast, the second slow: The half-lives of the precursors were about 3 and 10 hours, respectvely. Finally, a group of 16-and 17-kilodalton proteins was synthesized by cleavage of arge precursor proteins, likely in two steps. After cleavage, the proteins were not disulfide-bonded. The half-lfe of the precursors was short, less than 1 hour. In addition, for the 38-, 23-, and one of the 17-kilodalton proteins, a small decrease of relative molecular weight was observed as a last processing step. This was likely due to deglycosylation.Numerous studies have been carried out on the synthesis of storage proteins in ripening seeds (for reviews, see 6, 23). It has been found that in many species storage proteins are not synthesized directly but by cleavage of high mol wt precursor proteins. The precursor proteins may undergo several co-and post-translational modifications before yielding the final storage proteins. First, comparison of in vivo and in vitro translation products showed that the latter are normally a few kD larger. Probably, in vivo, a signal peptide is removed co-translationally (7,19). Second, some storage proteins are glycosylated. It was shown for phaseolin in beans (3) and conglycinin in soybeans (24) that cotranslational glycosylation is followed by a second glycosylation step. Third, following synthesis, the precursor may undergo cleavage. It was found for legumin in peas (1 1, 25), glycinin in soybeans (1, 24, 27), and globulin in oats (5) that the precursor protein is split into two subunits which, after cleavage, remain connected by a disulfide bridge. It might be that, such as in the processing of pro-insulin in animals, a connecting peptide is excised (26). In peas the lower mol wt vicilin subunits are also derived from large precursor proteins. After the s...

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Section: Discussionmentioning

confidence: 73%

Biosynthesis of Storage Proteins in Ripening Agrostemma githago L. Seeds

Klerk

1984

Plant Physiol.

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“…The storage proteins of legume seeds are synthesized on polysomes attached to the endoplasmic reticulum (ER) [5], enter the lumen of the ER [2,23], transit the Golgi apparatus [I0] and are deposited in membrane-bound vacuolar protein bodies 1-5/~m in diameter [4]. The storage proteins of legume seeds are synthesized on polysomes attached to the endoplasmic reticulum (ER) [5], enter the lumen of the ER [2,23], transit the Golgi apparatus [I0] and are deposited in membrane-bound vacuolar protein bodies 1-5/~m in diameter [4].…”

Section: Introductionmentioning

confidence: 99%

A modified storage protein is synthesized, processed, and degraded in the seeds of transgenic plants

Hoffman¹,

Donaldson²,

Herman³

1988

Plant Mol Biol

148

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In vitro mutagenesis was used to supplement the sulfur amino acid codon content of a gene encoding β-phaseolin, a Phaseolus vulgaris storage protein. The number of methionine codons in the phaseolin gene was increased from three to nine by insertion of a 45 base pair (bp) synthetic duplex. Either modified or normal phaseolin genes were integrated into the genome of tobacco plants through Agrobacterium tumefaciens-mediated transformation. Although similar levels of phaseolin RNA are detected in seeds of plants transformed with either the normal or modified (himet) gene, the quantity of himet protein is consistently much lower than normal β-phaseolin. Himet phaseolin is expressed in a temporal- and organ-specific fashion, and is N-glycosylated and assembled into trimers in the manner of normal phaseolin. After germination, both types of phaseolin are hydrolyzed, but the himet protein is more quickly degraded. Electron microscopic immunocytochemical observations of developing seeds indicate that the himet protein is primarily localized in the endoplasmic reticulum (ER) and in Golgi apparatus secretion vesicles. Himet phaseolin is absent from protein storage vacuoles, termed protein bodies, where normal phaseolin is deposited in transgenic tobacco. We interpret the immunocytochemical data to indicate that himet phasolin is transported through the ER and Golgi apparatus and is then degraded in Golgi secretion vesicles or the protein bodies.

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“…= apparent molecular weight; SDS = sodium dodecyl sulphate; SDS-PAGE = sodium dodecyl sulphate polyacrylamide gel electrophoresis. endoplasmic reticulum (7,9,10,15,16,28,42). Similar to the pathway for secretory proteins of animal cells, the storage protein polypeptides of plant seeds are synthesized as higher molecular weight precursors which are vectorially discharged into the lumen of the endoplasmic reticulum concomittantly with the cleavage of the signal peptide (10,15,16,25,48).…”

Section: Introductionmentioning

confidence: 99%

“…For elucidation of precursor processing of storage proteins in homologous systems, initially membrane bound polysomes or mRNA were supplemented with stripped microsome membranes which processed the newly synthesized precursor polypeptides to their mature form (12,15). Processing has also been observed when rough microsomes were used to direct cell-free protein biosynthesis (10,28,48).…”

Section: Introductionmentioning

confidence: 99%

Species specific signal peptide cleavage of plant storage protein precursors in the endoplasmic reticulum

Weber¹,

Brandt

1985

Carlsberg Res. Commun.

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Smooth microsomal membranes were isolated from immature cotyledons ofVicia faba and Phaseolus vulgaris as well as from immature endosperms of Bomi barley and its mutant lys 3a. Isolated Bomi barley endosperm polysomes direct the synthesis of hordein precursor polypeptides. Functional reconstitution of Bomi barley rough microsomes employing such polysomes and smooth microsomal membranes resulted in the ability of the membranes to perform signal peptide cleavage and co-translational transport of hordein precursor polypeptides into the lumen of the microsomes. Only a small portion of the hordein precursor polypeptides was processed and transported when the reconstitution was performed with smooth microsomal membranes isolated from cotyledons of Vicia faba and Phaseolus vulgaris or from the endosperms oflys 3a. A precursor polypeptide to the 50 kD vicilin was translated in vitro from mRNA of immature Vicia faba cotyledons. In the presence of Vicia faba smooth microsomal membranes the precursor polypeptide was co-translationally processed to the size of the polypeptide synthesized by rough microsomal membranes. Smooth microsomal membranes from cotyledons of Phaseolus vulgaris and from the endosperms of Bomi or lys 3a barley failed to process detectable amounts of the vicilin precursor polypeptide. Dog pancreatic microsomal membranes cleaved significant amounts of the hordein precursor polypeptides whereas only a small portion of the vicilin precursor polypeptides was processed.

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Sequestration of Pea Reserve Proteins by Rough Microsomes

Cited by 16 publications

References 21 publications

Biosynthesis of Storage Proteins in Ripening Agrostemma githago L. Seeds

Biosynthesis of Storage Proteins in Ripening Agrostemma githago L. Seeds

A modified storage protein is synthesized, processed, and degraded in the seeds of transgenic plants

Species specific signal peptide cleavage of plant storage protein precursors in the endoplasmic reticulum

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