Cell walls hydroxyproline-rich glycoprotein

Several of the hydroxyproline-rich glycoproteins extracted from plant tissues have carbohydrate-binding activity these glycoproteins have the characteristics of lectins. These lectins or lectin-like glycoproteins have compositions which are similar to that of the cell wall hydroxyproline-rich glycoprotein. 

Cassab, G.I., Nieto-Sotelo, J., Cooper, J.B., Van Holst, G.-J. Varner, J.E. (1985). A developmentally regulated hydroxyproline-rich glycoprotein from the cell walls of soybean coats. Plant Physiology, 77, 532-5. 

Proline is the only protein imino acid. In some proteins, proline is post-translationally hydroxylated to hydroxyproline. Such modifications occur to a large extent in hydroxyproline-rich glycoproteins (HPRG), which are involved in cell wall construction (Moore et al, 1991). Apart from the presence of proline in proteins, this amino acid also occurs in significant concentrations... 

Deposition of callose, gums, phenolics and polyphenolics in and around infected cells. Increases in hydroxyproline-rich glycoproteins in cell walls (, , , , )... 

Esquerre-Tugaye, M. T, Lafitte, C., Mazau, D., Toppan, A., and Touze, A., 1979, Cell surfaces in plant-microorganism interactions. II. Evidence for the accumulation of hydroxyproline-rich glycoproteins in the cell wall of diseased plants as a defense mechanism. Plant Physiol. 64 320-326. 

Hydroxyproline-rich glycoproteins are among the most prominent proteins in cell walls. The hydroxylation of proline is one of over 100 post-translational modifications that can occur on amino acid residues in protein (137). As a result of protein turnover (31) and cell stress, sometimes these amino acids may be found in extracellular matrices. 

Plants contain at least three classes of hydroxyproline-rich glycoproteins 1) the cell wall proteins, 2) the arabinogalactan proteins, and 3) lectins. According to Cooper and Varner (23) the hydroxyproline-rich glycoprotein of the cell wall of carrots is secreted from the cytoplasm as a soluble monomer that slowly becomes insolubilized. 

Hood, E. E., Shen, Q. X., and Varner, J. E. A developmentally regulated hydroxyproline-rich glycoprotein in maize pericarp cell walls. Plant Physiology, 138-142, ISSN 1532-2548 (1988). 

D. Is the Hydroxyproline-Rich Glycoprotein of the Cell Wall Connected to the... 

The covalent attachment of arabinose and galactose to the hydroxy-proline-rich proteins of primary cell walls is a generally accepted fact (83,85). However, the available evidence suggests that the hydroxyproline-rich glycoprotein is not covalently attached to any of the other cell wall polymers. The evidence does not rule out the possible existence of strong, non-covalent bonding between the hydroxyproline-rich glycoprotein and the other wall polymers. 

There is no evidence which demonstrates a covalent linkage between the hydroxyproline-rich glycoprotein and the polysaccharides of cell walls. The hydroxyproline-rich glycoprotein which is present in the culture medium of sycamore cells grown in suspension culture has been... 

There are four major types of polymers in the primary cell walls of dicots hydroxyproline-rich glycoprotein, cellulose, hemicellulose and pectic polysaccharides. The mole percents of these polymers in suspension-cultured sycamore cell walls is presented in Table 8 (45, 75). The pectic polysaccharides are covalently interconnected. The hemicelluloses are non-covalently bonded to the cellulose fibers. There is no known attachment between the hydroxyproline-rich glycoprotein and the other cell wall polymers. The extent of covalent attachment between the hemicelluloses and the pectic polysaccharides is unknown. The fact that removal of the xyloglucans from the cell walls is enhanced by solubilization of the pectic polysaccharides (31, 75, 123) suggests that... 

The basic extensins. These are hydroxyproline-, lysine- and tyrosine-rich glycoproteins consisting of rigid molecular rods about 80 nm long (14,15), bearing short mono- to tetrasaccharide side-chains (2,14). When newly secreted they bind ionically to the acidic polysaccharides of the cell wall and can be extracted with cold salt solutions later they become much more resistant to salt-extraction and are said to be covalently bound, probably via dimerization of their tyrosine residues to form isodityrosine (15). 

Although the principal cell wall components of plants are carbohydrates, proteins account for 5-10% of the mass.165 Predominant among these are glycoprotein extensins. Like collagen, they are rich in 4-hydroxyproline which is glycosylated with arabi-nose oligosaccharides and galactose (p. 181). Other... 

M. J. Kieliszewski, M. O Neill, J. Leykam. R. Orlando. Tandem mass spectrometry and structural elucidation of glycopeptides from a hydroxyproline-rich plant cell wall glycoprotein indicate that contiguous hydroxyproline residues are the major sites of hydroxyproline O-arabinosylation. Jour. Biol. Chem. 1995,270, 2541-2549. 

Further the protein content of the AIR varies with the maturity of the tissues, high in immature and low in mature tissues. Since pronase tends to degrade some of the hydroxyproline (hyp)-poor cell wall glycoproteins and possibly portions of the hyp-rich glycoproteins, pronase-treated residues may not give as much useful information on wall glycoproteins compared with the alternative methods described in this article. 

Partial alkaline degradations have been used for the release of glycopep-tides from the hydroxyproline-rich cell wall glycoprotein(s). Lamport... 

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