Post-Translational Modifications

Beevers, Leonard

doi:10.1007/978-3-642-68237-7_5

Cited by 13 publications

(5 citation statements)

References 141 publications

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“…Asn-linked oligosaccharides are usually rich in mannose [18] which is consistent with the observation of Con-A binding in these proteins. Since no hydroxyproline was found in the 28 kDa protein [5], it is unlikely that arabinosyl linkages of the type found in the cell-wall glycoprotein extensin [3] occur in these proteins. Fig.…”

Section: D N a Sequence Analysismentioning

confidence: 99%

Proteins homologous to leaf glycoproteins are abundant in stems of dark-grown soybean seedlings. Analysis of proteins and cDNAs

et al. 1988

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We report here the cloning and sequence analysis of cDNAs for a pair of closely related proteins from soybean (Glycine max [L.] Merr. cv. Williams 82) stems. Both proteins are abundant in soluble extracts of seedling stems but not of roots. One of these proteins (M r=28 kDa) is also foundd in the cell wall fraction of stems and actumulates there when seedlings are exposed to mild water deficit for 48 h. The mRNA for these proteins is most abundant in the stem region which contains dividing cells, less abundant in elongating and mature stem cells, and rare in roots. Using antiserum against the 28 kDa protein, we isolated cDNA clones encoding it and an antigenically related 31 kDa protein. The two cDNAs are 80% homologous in nucleotide and amino acid coding sequence. The predicted proteins have similar hydropathy profiles, and contain putative NH2-terminal signal sequences and a single putative N-linked glycosylation site. The two proteins differ significantly in calculated pI (28 kDa=8.6; 31 kDa=5.8), and the charge difference is demonstrated on two-dimensional gels. The proteins described here may function as somatic storage proteins during early seedling development, and are closely related to glycoproteins which accumulate in vacuoles of paraveinal mesophyll cells of fully expanded soybean leaves when plants are depodded.

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Section: D N a Sequence Analysismentioning

confidence: 99%

Proteins homologous to leaf glycoproteins are abundant in stems of dark-grown soybean seedlings. Analysis of proteins and cDNAs

et al. 1988

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“…There is mounting evidence that metal complexes which show some similarities to MTs also occur in angiosperms, and the suggestion that such compounds may function to complex potentially toxic metal ions in plants is gaining recognition (Beevers 1982, Woolhouse 1983. Amino acid compositions of some partially purified complexes have certain features in common with MT (Rauser and Curvetto 1980, Rauser et al 1983, Lolkema et al 1984, Wagner 1984, Robinson and Thurman 1985.…”

Section: Introductionmentioning

confidence: 99%

“Metallothionein‐like” metal complexes in angiosperms; their structure and function

Robinson¹,

Jackson²

1986

Physiologia Plantarum

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Evidence for the presence of the metal‐binding protein metallothionein, MT, in higher plants is equivocal. Although a number of MT‐like metal complexes have been isolated from plants, the chemical structures of most of these compounds have not been fully elucidated. Recently a novel class of plant peptides, poly (γ‐glutamylcysteinyl) glycines, (γEC)nG, have been discovered. These peptides bind metal ions, and in the presence of such ions the amount of (γEC), G in plant cells increases. The presence of peptide bonds through the γ‐carboxyl group of glutamate, rather than the α‐carboxyl group, suggests that these peptides are not encoded by structural genes but are the products of biosynthetic pathways. Cells which are resistant to supra‐optimal concentrations of certain metal ions over‐produce (γEC)n G. (γEC)n G. may be functional analogues of MT. Whether or not some plants also produce MT is an important question which remains to be answered.

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“…One ml containing 50,000 units of PMH was applied and washed through with 25 ml buffer B followed by elution with 10 ml of buffer B containing 10 mM glucose-6-P, 10 ml mannose-1-P, and 10 mM mannose-6-P, respectively. Fractions of 5 ml (1)(2)(3)(4)(5) and I ml were collected. contained bound phosphomannosylated enzymes from D. discoideum secretions, retained a single protein from bovine liver acetone powder extracts which could be specifically eluted by mannose-6-P (results not shown).…”

Section: Resultsmentioning

confidence: 99%

“…An oligosaccharide containing two glucosamine, nine mannose, and three glucose residues attached to a dolichol carrier is first synthesized and then transferred en bloc to a polypeptide chain (2). The oligosaccharide is subsequently processed by removal of the terminal glucose residues and some of the mannose residues followed by addition of other sugar residues such as galactose, fucose, and Nacetylglucosamine.…”

Section: Discussionmentioning

confidence: 99%

Protein Bodies and Vacuoles as Lysosomes

Gaudreault

Beevers²

1984

Plant Physiol.

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We have failed to detect the presence of mannose-6-phosphate In the olgsaccharide moiety of glycoproteins from pea (Pismum stivm L. cv Burpeesn) cotyledons sing an asay system sensitive to 10 picomoles of aos6osphate. We were also unable to demonstrate any reten tion of glycosidase activity from pea seedlings and pea cotyledons on Sephaose-cpled phosphon yl receptor proteins isolted from bovine liver which were, however, able to In living cells, intracellular digestive processes carried out by hydrolytic enzymes (proteinases, glycosidases, nucleases) are spatially separated from sites ofbiosynthesis such as the ER and the cytoplasm. In animal systems this is achieved by compartmentation ofunspecific hydrolases into lysosomes (1). The search for an analogous organelle in plants subsequently revealed that vacuoles in leaves and protein bodies in cotylodons both contain the required mixed complement of hydrolakes to function efficiently as the plant lysosomes (17, 27).We are currently interested in the mechanism which controls the proper routing of hydrolases from their site of synthesis into digestive organelles. Extending the analogy between lysosomes and vacuoles or protein bodies beyond the functional level, we first established that hydrolases from pea are, like their animal counterparts, glycosylated (15). In animal systems the targeting of hydrolases from the ER to the lysosomes is mediated by mannose-6-phosphate residues attached to the oligosaccharide moiety of these enzymes and its interaction with a membranebound lectin receptor specific for mannose-6-P (9, 25).Based on the results from experiments designed along the lines of those used to successfully demonstrate the key role played by mannose-6-P in intracellular transport of lysosomal enzymes in animals, we conclude that a similar mechanism does not appear to be operating in pea cotyledons.'Supported by National Science Foundation Grant PCM 82-04537. Bradford (3) with BSA as the standard. ER-associated glycosidic activity was determined with nitrophenyl substrates as described previously (15). D. discoideum (l-N-acetylglucosaminidase (hexosaminidase) activity was measured at pH 5.0 according to Every and Ashworth (8). One unit of hexosaminidase was defined as the amount of enzyme which catalyzed the release of 1 grmol of nitrophenol h-'.Preparation of Membrane Fractions. Pea cotyledons were homogenized and organelle enriched fractions were obtained by differential centrifugation as described by Nagahashi and Beevers (18). The grinding mixture was 0.5 M sucrose, 5 mM 2-mercaptoethanol, 30 mm Tris-Mes (pH 7.0), and the buffered sucrose consisted of 0.25 M sucrose, 1 mM 2-mercaptoethanol, 1 mM Tris-Mes (pH 7.0). Three centrifugations were performed 1,000g 5 min (cell wall and starch grains)-l 3,000g 15 min (mitochondrial enriched 13K pellet), and 40,000g 35 min (ER enriched 40K microsomal pellet).The 40K pellets were rinsed once in the grinding mixture followed by centrifugation at the 40,000g force for 30 min.The ER cistemae from the 40K pel...

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Post-Translational Modifications

Cited by 13 publications

References 141 publications

Proteins homologous to leaf glycoproteins are abundant in stems of dark-grown soybean seedlings. Analysis of proteins and cDNAs

Proteins homologous to leaf glycoproteins are abundant in stems of dark-grown soybean seedlings. Analysis of proteins and cDNAs

“Metallothionein‐like” metal complexes in angiosperms; their structure and function

Protein Bodies and Vacuoles as Lysosomes

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